Programs & Examples On #Server tags

How to list active connections on PostgreSQL?

Following will give you active connections/ queries in postgres DB-

FROM pg_stat_activity
WHERE state = 'active';

You may use 'idle' instead of active to get already executed connections/queries.

How to replicate background-attachment fixed on iOS

It has been asked in the past, apparently it costs a lot to mobile browsers, so it's been disabled.

Check this comment by @PaulIrish:

Fixed-backgrounds have huge repaint cost and decimate scrolling performance, which is, I believe, why it was disabled.

you can see workarounds to this in this posts:

Fixed background image with ios7

Fixed body background scrolls with the page on iOS7

Setting Curl's Timeout in PHP

You can't run the request from a browser, it will timeout waiting for the server running the CURL request to respond. The browser is probably timing out in 1-2 minutes, the default network timeout.

You need to run it from the command line/terminal.

How to solve SQL Server Error 1222 i.e Unlock a SQL Server table

I had these SQL behavior settings enabled on options query execution: ANSI SET IMPLICIT_TRANSACTIONS checked. On execution of your query e.g create, alter table or stored procedure, you have to COMMIT it.

Just type COMMIT and execute it F5

HTML input file selection event not firing upon selecting the same file

Clearing the value of 0th index of input worked for me. Please try the below code, hope this will work (AngularJs).

          scope.onClick = function() {
            input[0].value = "";

Trying to get property of non-object MySQLi result

$sql = "SELECT * FROM table";
$result = $conn->query($sql);

if (!$result) {
    trigger_error('Invalid query: ' . $conn->error);

check the error with mysqli_error() function

probably your query has some faults.

Could not open a connection to your authentication agent

Even I was getting "Could not open a connection to your authentication agent." on running the command while generating and adding SSH key: ssh-add ~/.ssh/id_rsa. I resolved it by stopping the multiple ssh-agent instances running on my machine and then uninstalled the Git from control panel on my windows machine and then again installed Git and things were working now.

Why do we have to normalize the input for an artificial neural network?

The reason normalization is needed is because if you look at how an adaptive step proceeds in one place in the domain of the function, and you just simply transport the problem to the equivalent of the same step translated by some large value in some direction in the domain, then you get different results. It boils down to the question of adapting a linear piece to a data point. How much should the piece move without turning and how much should it turn in response to that one training point? It makes no sense to have a changed adaptation procedure in different parts of the domain! So normalization is required to reduce the difference in the training result. I haven't got this written up, but you can just look at the math for a simple linear function and how it is trained by one training point in two different places. This problem may have been corrected in some places, but I am not familiar with them. In ALNs, the problem has been corrected and I can send you a paper if you write to wwarmstrong AT

Python and JSON - TypeError list indices must be integers not str

I solved changing




What causes javac to issue the "uses unchecked or unsafe operations" warning

If you do what it suggests and recompile with the "-Xlint:unchecked" switch, it will give you more detailed information.

As well as the use of raw types (as described by the other answers), an unchecked cast can also cause the warning.

Once you've compiled with -Xlint, you should be able to rework your code to avoid the warning. This is not always possible, particularly if you are integrating with legacy code that cannot be changed. In this situation, you may decide to suppress the warning in places where you know that the code is correct:

public void myMethod()

How to upgrade all Python packages with pip

One line in cmd:

for /F "delims= " %i in ('pip list --outdated --format=legacy') do pip install -U %i

So a

pip check

afterwards should make sure no dependencies are broken.

Write in body request with HttpClient

If your xml is written by java.lang.String you can just using HttpClient in this way

    public void post() throws Exception{
        HttpClient client = new DefaultHttpClient();
        HttpPost post = new HttpPost("");
        String xml = "<xml>xxxx</xml>";
        HttpEntity entity = new ByteArrayEntity(xml.getBytes("UTF-8"));
        HttpResponse response = client.execute(post);
        String result = EntityUtils.toString(response.getEntity());

pay attention to the Exceptions.

BTW, the example is written by the httpclient version 4.x

Check whether values in one data frame column exist in a second data frame

Use %in% as follows

A$C %in% B$C

Which will tell you which values of column C of A are in B.

What is returned is a logical vector. In the specific case of your example, you get:

A$C %in% B$C

Which you can use as an index to the rows of A or as an index to A$C to get the actual values:

# as a row index
A[A$C %in% B$C,  ]  # note the comma to indicate we are indexing rows

# as an index to A$C
A$C[A$C %in% B$C]
[1] 1 3 4  # returns all values of A$C that are in B$C

We can negate it too:

A$C[!A$C %in% B$C]
[1] 2   # returns all values of A$C that are NOT in B$C

If you want to know if a specific value is in B$C, use the same function:

  2 %in% B$C   # "is the value 2 in B$C ?"  

  A$C[2] %in% B$C  # "is the 2nd element of A$C in B$C ?"  

SQL grammar for SELECT MIN(DATE)

You need to use GROUP BY instead of DISTINCT if you want to use aggregation functions.

SELECT title, MIN(date)
FROM table
GROUP BY title

Getting and removing the first character of a string

See ?substring.

x <- 'hello stackoverflow'
substring(x, 1, 1)
## [1] "h"
substring(x, 2)
## [1] "ello stackoverflow"

The idea of having a pop method that both returns a value and has a side effect of updating the data stored in x is very much a concept from object-oriented programming. So rather than defining a pop function to operate on character vectors, we can make a reference class with a pop method.

PopStringFactory <- setRefClass(
  fields = list(
    x = "character"  
  methods = list(
    initialize = function(x)
      x <<- x
    pop = function(n = 1)
      if(nchar(x) == 0)
        warning("Nothing to pop.")
      first <- substring(x, 1, n)
      x <<- substring(x, n + 1)

x <- PopStringFactory$new("hello stackoverflow")
## Reference class object of class "PopString"
## Field "x":
## [1] "hello stackoverflow"
replicate(nchar(x$x), x$pop())
## [1] "h" "e" "l" "l" "o" " " "s" "t" "a" "c" "k" "o" "v" "e" "r" "f" "l" "o" "w"

How do I access named capturing groups in a .NET Regex?

Additionally if someone have a use case where he needs group names before executing search on Regex object he can use:

var regex = new Regex(pattern); // initialized somewhere
// ...
var groupNames = regex.GetGroupNames();

Change visibility of ASP.NET label with JavaScript

You need to be wary of XSS when doing stuff like this:

document.getElementById('<%= Label1.ClientID %>').style.display

The chances are that no-one will be able to tamper with the ClientID of Label1 in this instance, but just to be on the safe side you might want pass it's value through one of the AntiXss library's methods:

document.getElementById('<%= AntiXss.JavaScriptEncode(Label1.ClientID) %>').style.display

When should I use File.separator and when File.pathSeparator? class contains four static separator variables. For better understanding, Let's understand with the help of some code

  1. separator: Platform dependent default name-separator character as String. For windows, it’s ‘\’ and for unix it’s ‘/’
  2. separatorChar: Same as separator but it’s char
  3. pathSeparator: Platform dependent variable for path-separator. For example PATH or CLASSPATH variable list of paths separated by ‘:’ in Unix systems and ‘;’ in Windows system
  4. pathSeparatorChar: Same as pathSeparator but it’s char

Note that all of these are final variables and system dependent.

Here is the java program to print these separator variables.


public class FileSeparator {

    public static void main(String[] args) {
        System.out.println("File.separator = "+File.separator);
        System.out.println("File.separatorChar = "+File.separatorChar);
        System.out.println("File.pathSeparator = "+File.pathSeparator);
        System.out.println("File.pathSeparatorChar = "+File.pathSeparatorChar);


Output of above program on Unix system:

File.separator = /
File.separatorChar = /
File.pathSeparator = :
File.pathSeparatorChar = :

Output of the program on Windows system:

File.separator = \
File.separatorChar = \
File.pathSeparator = ;
File.pathSeparatorChar = ;

To make our program platform independent, we should always use these separators to create file path or read any system variables like PATH, CLASSPATH.

Here is the code snippet showing how to use separators correctly.

//no platform independence, good for Unix systems
File fileUnsafe = new File("tmp/abc.txt");
//platform independent and safe to use across Unix and Windows
File fileSafe = new File("tmp"+File.separator+"abc.txt");

What is TypeScript and why would I use it in place of JavaScript?

TypeScript's relation to JavaScript

TypeScript is a typed superset of JavaScript that compiles to plain JavaScript -

JavaScript is a programming language that is developed by EMCA's Technical Committee 39, which is a group of people composed of many different stakeholders. TC39 is a committee hosted by ECMA: an internal standards organization. JavaScript has many different implementations by many different vendors (e.g. Google, Microsoft, Oracle, etc.). The goal of JavaScript is to be the lingua franca of the web.

TypeScript is a superset of the JavaScript language that has a single open-source compiler and is developed mainly by a single vendor: Microsoft. The goal of TypeScript is to help catch mistakes early through a type system and to make JavaScript development more efficient.

Essentially TypeScript achieves its goals in three ways:

  1. Support for modern JavaScript features - The JavaScript language (not the runtime) is standardized through the ECMAScript standards. Not all browsers and JavaScript runtimes support all features of all ECMAScript standards (see this overview). TypeScript allows for the use of many of the latest ECMAScript features and translates them to older ECMAScript targets of your choosing (see the list of compile targets under the --target compiler option). This means that you can safely use new features, like modules, lambda functions, classes, the spread operator and destructuring, while remaining backwards compatible with older browsers and JavaScript runtimes.

  2. Advanced type system - The type support is not part of the ECMAScript standard and will likely never be due to the interpreted nature instead of compiled nature of JavaScript. The type system of TypeScript is incredibly rich and includes: interfaces, enums, hybrid types, generics, union/intersection types, access modifiers and much more. The official website of TypeScript gives an overview of these features. Typescript's type system is on-par with most other typed languages and in some cases arguably more powerful.

  3. Developer tooling support - TypeScript's compiler can run as a background process to support both incremental compilation and IDE integration such that you can more easily navigate, identify problems, inspect possibilities and refactor your codebase.

TypeScript's relation to other JavaScript targeting languages

TypeScript has a unique philosophy compared to other languages that compile to JavaScript. JavaScript code is valid TypeScript code; TypeScript is a superset of JavaScript. You can almost rename your .js files to .ts files and start using TypeScript (see "JavaScript interoperability" below). TypeScript files are compiled to readable JavaScript, so that migration back is possible and understanding the compiled TypeScript is not hard at all. TypeScript builds on the successes of JavaScript while improving on its weaknesses.

On the one hand, you have future proof tools that take modern ECMAScript standards and compile it down to older JavaScript versions with Babel being the most popular one. On the other hand, you have languages that may totally differ from JavaScript which target JavaScript, like CoffeeScript, Clojure, Dart, Elm, Haxe, Scala.js, and a whole host more (see this list). These languages, though they might be better than where JavaScript's future might ever lead, run a greater risk of not finding enough adoption for their futures to be guaranteed. You might also have more trouble finding experienced developers for some of these languages, though the ones you will find can often be more enthusiastic. Interop with JavaScript can also be a bit more involved, since they are farther removed from what JavaScript actually is.

TypeScript sits in between these two extremes, thus balancing the risk. TypeScript is not a risky choice by any standard. It takes very little effort to get used to if you are familiar with JavaScript, since it is not a completely different language, has excellent JavaScript interoperability support and it has seen a lot of adoption recently.

Optionally static typing and type inference

JavaScript is dynamically typed. This means JavaScript does not know what type a variable is until it is actually instantiated at run-time. This also means that it may be too late. TypeScript adds type support to JavaScript and catches type errors during compilation to JavaScript. Bugs that are caused by false assumptions of some variable being of a certain type can be completely eradicated if you play your cards right (how strict you type your code or if you type your code at all is up to you).

TypeScript makes typing a bit easier and a lot less explicit by the usage of type inference. For example: var x = "hello" in TypeScript is the same as var x : string = "hello". The type is simply inferred from its use. Even it you don't explicitly type the types, they are still there to save you from doing something which otherwise would result in a run-time error.

TypeScript is optionally typed by default. For example function divideByTwo(x) { return x / 2 } is a valid function in TypeScript which can be called with any kind of parameter, even though calling it with a string will obviously result in a runtime error. Just like you are used to in JavaScript. This works, because when no type was explicitly assigned and the type could not be inferred, like in the divideByTwo example, TypeScript will implicitly assign the type any. This means the divideByTwo function's type signature automatically becomes function divideByTwo(x : any) : any. There is a compiler flag to disallow this behavior: --noImplicitAny. Enabling this flag gives you a greater degree of safety, but also means you will have to do more typing.

Types have a cost associated with them. First of all, there is a learning curve, and second of all, of course, it will cost you a bit more time to set up a codebase using proper strict typing too. In my experience, these costs are totally worth it on any serious codebase you are sharing with others. A Large Scale Study of Programming Languages and Code Quality in Github suggests that "statically typed languages, in general, are less defect prone than the dynamic types, and that strong typing is better than weak typing in the same regard".

It is interesting to note that this very same paper finds that TypeScript is less error-prone than JavaScript:

For those with positive coefficients we can expect that the language is associated with, ceteris paribus, a greater number of defect fixes. These languages include C, C++, JavaScript, Objective-C, Php, and Python. The languages Clojure, Haskell, Ruby, Scala, and TypeScript, all have negative coefficients implying that these languages are less likely than the average to result in defect fixing commits.

Enhanced IDE support

The development experience with TypeScript is a great improvement over JavaScript. The IDE is informed in real-time by the TypeScript compiler on its rich type information. This gives a couple of major advantages. For example, with TypeScript, you can safely do refactorings like renames across your entire codebase. Through code completion, you can get inline help on whatever functions a library might offer. No more need to remember them or look them up in online references. Compilation errors are reported directly in the IDE with a red squiggly line while you are busy coding. All in all, this allows for a significant gain in productivity compared to working with JavaScript. One can spend more time coding and less time debugging.

There is a wide range of IDEs that have excellent support for TypeScript, like Visual Studio Code, WebStorm, Atom and Sublime.

Strict null checks

Runtime errors of the form cannot read property 'x' of undefined or undefined is not a function are very commonly caused by bugs in JavaScript code. Out of the box TypeScript already reduces the probability of these kinds of errors occurring, since one cannot use a variable that is not known to the TypeScript compiler (with the exception of properties of any typed variables). It is still possible though to mistakenly utilize a variable that is set to undefined. However, with the 2.0 version of TypeScript you can eliminate these kinds of errors all together through the usage of non-nullable types. This works as follows:

With strict null checks enabled (--strictNullChecks compiler flag) the TypeScript compiler will not allow undefined to be assigned to a variable unless you explicitly declare it to be of nullable type. For example, let x : number = undefined will result in a compile error. This fits perfectly with type theory since undefined is not a number. One can define x to be a sum type of number and undefined to correct this: let x : number | undefined = undefined.

Once a type is known to be nullable, meaning it is of a type that can also be of the value null or undefined, the TypeScript compiler can determine through control flow based type analysis whether or not your code can safely use a variable or not. In other words when you check a variable is undefined through for example an if statement the TypeScript compiler will infer that the type in that branch of your code's control flow is not anymore nullable and therefore can safely be used. Here is a simple example:

let x: number | undefined;
if (x !== undefined) x += 1; // this line will compile, because x is checked.
x += 1; // this line will fail compilation, because x might be undefined.

During the build, 2016 conference co-designer of TypeScript Anders Hejlsberg gave a detailed explanation and demonstration of this feature: video (from 44:30 to 56:30).


To use TypeScript you need a build process to compile to JavaScript code. The build process generally takes only a couple of seconds depending of course on the size of your project. The TypeScript compiler supports incremental compilation (--watch compiler flag) so that all subsequent changes can be compiled at greater speed.

The TypeScript compiler can inline source map information in the generated .js files or create separate .map files. Source map information can be used by debugging utilities like the Chrome DevTools and other IDE's to relate the lines in the JavaScript to the ones that generated them in the TypeScript. This makes it possible for you to set breakpoints and inspect variables during runtime directly on your TypeScript code. Source map information works pretty well, it was around long before TypeScript, but debugging TypeScript is generally not as great as when using JavaScript directly. Take the this keyword for example. Due to the changed semantics of the this keyword around closures since ES2015, this may actually exists during runtime as a variable called _this (see this answer). This may confuse you during debugging but generally is not a problem if you know about it or inspect the JavaScript code. It should be noted that Babel suffers the exact same kind of issue.

There are a few other tricks the TypeScript compiler can do, like generating intercepting code based on decorators, generating module loading code for different module systems and parsing JSX. However, you will likely require a build tool besides the Typescript compiler. For example, if you want to compress your code you will have to add other tools to your build process to do so.

There are TypeScript compilation plugins available for Webpack, Gulp, Grunt and pretty much any other JavaScript build tool out there. The TypeScript documentation has a section on integrating with build tools covering them all. A linter is also available in case you would like even more build time checking. There are also a great number of seed projects out there that will get you started with TypeScript in combination with a bunch of other technologies like Angular 2, React, Ember, SystemJS, Webpack, Gulp, etc.

JavaScript interoperability

Since TypeScript is so closely related to JavaScript it has great interoperability capabilities, but some extra work is required to work with JavaScript libraries in TypeScript. TypeScript definitions are needed so that the TypeScript compiler understands that function calls like _.groupBy or angular.copy or $.fadeOut are not in fact illegal statements. The definitions for these functions are placed in .d.ts files.

The simplest form a definition can take is to allow an identifier to be used in any way. For example, when using Lodash, a single line definition file declare var _ : any will allow you to call any function you want on _, but then, of course, you are also still able to make mistakes: _.foobar() would be a legal TypeScript call, but is, of course, an illegal call at run-time. If you want proper type support and code completion your definition file needs to to be more exact (see lodash definitions for an example).

Npm modules that come pre-packaged with their own type definitions are automatically understood by the TypeScript compiler (see documentation). For pretty much any other semi-popular JavaScript library that does not include its own definitions somebody out there has already made type definitions available through another npm module. These modules are prefixed with "@types/" and come from a Github repository called DefinitelyTyped.

There is one caveat: the type definitions must match the version of the library you are using at run-time. If they do not, TypeScript might disallow you from calling a function or dereferencing a variable that exists or allow you to call a function or dereference a variable that does not exist, simply because the types do not match the run-time at compile-time. So make sure you load the right version of the type definitions for the right version of the library you are using.

To be honest, there is a slight hassle to this and it may be one of the reasons you do not choose TypeScript, but instead go for something like Babel that does not suffer from having to get type definitions at all. On the other hand, if you know what you are doing you can easily overcome any kind of issues caused by incorrect or missing definition files.

Converting from JavaScript to TypeScript

Any .js file can be renamed to a .ts file and ran through the TypeScript compiler to get syntactically the same JavaScript code as an output (if it was syntactically correct in the first place). Even when the TypeScript compiler gets compilation errors it will still produce a .js file. It can even accept .js files as input with the --allowJs flag. This allows you to start with TypeScript right away. Unfortunately, compilation errors are likely to occur in the beginning. One does need to remember that these are not show-stopping errors like you may be used to with other compilers.

The compilation errors one gets in the beginning when converting a JavaScript project to a TypeScript project are unavoidable by TypeScript's nature. TypeScript checks all code for validity and thus it needs to know about all functions and variables that are used. Thus type definitions need to be in place for all of them otherwise compilation errors are bound to occur. As mentioned in the chapter above, for pretty much any JavaScript framework there are .d.ts files that can easily be acquired with the installation of DefinitelyTyped packages. It might, however, be that you've used some obscure library for which no TypeScript definitions are available or that you've polyfilled some JavaScript primitives. In that case, you must supply type definitions for these bits for the compilation errors to disappear. Just create a .d.ts file and include it in the tsconfig.json's files array, so that it is always considered by the TypeScript compiler. In it declare those bits that TypeScript does not know about as type any. Once you've eliminated all errors you can gradually introduce typing to those parts according to your needs.

Some work on (re)configuring your build pipeline will also be needed to get TypeScript into the build pipeline. As mentioned in the chapter on compilation there are plenty of good resources out there and I encourage you to look for seed projects that use the combination of tools you want to be working with.

The biggest hurdle is the learning curve. I encourage you to play around with a small project at first. Look how it works, how it builds, which files it uses, how it is configured, how it functions in your IDE, how it is structured, which tools it uses, etc. Converting a large JavaScript codebase to TypeScript is doable when you know what you are doing. Read this blog for example on converting 600k lines to typescript in 72 hours). Just make sure you have a good grasp of the language before you make the jump.


TypeScript is open-source (Apache 2 licensed, see GitHub) and backed by Microsoft. Anders Hejlsberg, the lead architect of C# is spearheading the project. It's a very active project; the TypeScript team has been releasing a lot of new features in the last few years and a lot of great ones are still planned to come (see the roadmap).

Some facts about adoption and popularity:

  • In the 2017 StackOverflow developer survey TypeScript was the most popular JavaScript transpiler (9th place overall) and won third place in the most loved programming language category.
  • In the 2018 state of js survey TypeScript was declared as one of the two big winners in the JavaScript flavors category (with ES6 being the other).
  • In the 2019 StackOverlow deverloper survey TypeScript rose to the 9th place of most popular languages amongst professional developers, overtaking both C and C++. It again took third place amongst most the most loved languages.

How to make picturebox transparent?

Try using an ImageList

ImageList imgList = new ImageList;

imgList.TransparentColor = Color.White;

Load the image like this:

picturebox.Image = imgList.Images[img_index];

Replace invalid values with None in Pandas DataFrame

I prefer the solution using replace with a dict because of its simplicity and elegance:

df.replace({'-': None})

You can also have more replacements:

df.replace({'-': None, 'None': None})

And even for larger replacements, it is always obvious and clear what is replaced by what - which is way harder for long lists, in my opinion.

Error LNK2019: Unresolved External Symbol in Visual Studio

I was getting this error after adding the include files and linking the library. It was because the lib was built with non-unicode and my application was unicode. Matching them fixed it.

BeautifulSoup getText from between <p>, not picking up subsequent paragraphs

You are getting close!

# Find all of the text between paragraph tags and strip out the html
page = soup.find('p').getText()

Using find (as you've noticed) stops after finding one result. You need find_all if you want all the paragraphs. If the pages are formatted consistently ( just looked over one), you could also use something like


to zero in on the body of the article.

Passing parameters to a Bash function

A simple example that will clear both during executing script or inside script while calling a function.

echo "parameterized function example"
function print_param_value(){
    value1="${1}" # $1 represent first argument
    value2="${2}" # $2 represent second argument
    echo "param 1 is  ${value1}" # As string
    echo "param 2 is ${value2}"
    sum=$(($value1+$value2)) # Process them as number
    echo "The sum of two value is ${sum}"
print_param_value "6" "4" # Space-separated value
# You can also pass parameters during executing the script
print_param_value "$1" "$2" # Parameter $1 and $2 during execution

# Suppose our script name is "param_example".
# Call it like this:
# ./param_example 5 5
# Now the parameters will be $1=5 and $2=5

What is the current choice for doing RPC in Python?

You missed out omniORB. This is a pretty full CORBA implementation, so you can also use it to talk to other languages that have CORBA support.

JQuery, Spring MVC @RequestBody and JSON - making it work together

In Addition you also need to be sure that you have


in your SPring configuration xml.

I also would recommend you to read this blog post. It helped me alot. Spring blog - Ajax Simplifications in Spring 3.0


just checked my working code where I have @RequestBody working correctly. I also have this bean in my config:

<bean id="jacksonMessageConverter" class="org.springframework.http.converter.json.MappingJacksonHttpMessageConverter"></bean>
 <bean class="org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter">
<property name="messageConverters">
    <ref bean="jacksonMessageConverter"/>

May be it would be nice to see what Log4j is saying. it usually gives more information and from my experience the @RequestBody will fail if your request's content type is not Application/JSON. You can run Fiddler 2 to test it, or even Mozilla Live HTTP headers plugin can help.

How to access Winform textbox control from another class?

Form1 form = new Form1(); 
form.textBox1.Text = "test";

How to loop and render elements in React-native?

For initial array, better use object instead of array, as then you won't be worrying about the indexes and it will be much more clear what is what:

const initialArr = [{
    color: "blue",
    text: "text1"
}, {
    color: "red",
    text: "text2"

For actual mapping, use JS Array map instead of for loop - for loop should be used in cases when there's no actual array defined, like displaying something a certain number of times:

onPress = () => {

renderButtons() {
    return => {
        return (
                style={{ borderColor: item.color }}


render() {
    return (
        <View style={...}>

I moved the mapping to separate function outside of render method for more readable code. There are many other ways to loop through list of elements in react native, and which way you'll use depends on what do you need to do. Most of these ways are covered in this article about React JSX loops, and although it's using React examples, everything from it can be used in React Native. Please check it out if you're interested in this topic!

Also, not on the topic on the looping, but as you're already using the array syntax for defining the onPress function, there's no need to bind it again. This, again, applies only if the function is defined using this syntax within the component, as the arrow syntax auto binds the function.

Array of arrays (Python/NumPy)



tolist method mentioned above will return the nested Python list

How to use Lambda in LINQ select statement

Why not just use all Lambda syntax?

database.Stores.Where(s => s.CompanyID == curCompany.ID)
               .Select(s => new SelectListItem
                       Value = s.Name,
                       Text = s.ID

Creating a LinkedList class from scratch

If you're actually building a real system, then yes, you'd typically just use the stuff in the standard library if what you need is available there. That said, don't think of this as a pointless exercise. It's good to understand how things work, and understanding linked lists is an important step towards understanding more complex data structures, many of which don't exist in the standard libraries.

There are some differences between the way you're creating a linked list and the way the Java collections API does it. The Collections API is trying to adhere to a more complicated interface. The Collections API linked list is also a doubly linked list, while you're building a singly linked list. What you're doing is more appropriate for a class assignment.

With your LinkedList class, an instance will always be a list of at least one element. With this kind of setup you'd use null for when you need an empty list.

Think of next as being "the rest of the list". In fact, many similar implementations use the name "tail" instead of "next".

Here's a diagram of a LinkedList containing 3 elements:

linked list diagram

Note that it's a LinkedList object pointing to a word ("Hello") and a list of 2 elements. The list of 2 elements has a word ("Stack") and a list of 1 element. That list of 1 element has a word ("Overflow") and an empty list (null). So you can treat next as just another list that happens to be one element shorter.

You may want to add another constructor that just takes a String, and sets next to null. This would be for creating a 1-element list.

To append, you check if next is null. If it is, create a new one element list and set next to that.

next = new LinkedList(word);

If next isn't null, then append to next instead.


This is the recursive approach, which is the least amount of code. You can turn that into an iterative solution which would be more efficient in Java*, and wouldn't risk a stack overflow with very long lists, but I'm guessing that level of complexity isn't needed for your assignment.

* Some languages have tail call elimination, which is an optimization that lets the language implementation convert "tail calls" (a call to another function as the very last step before returning) into (effectively) a "goto". This makes such code completely avoid using the stack, which makes it safer (you can't overflow the stack if you don't use the stack) and typically more efficient. Scheme is probably the most well known example of a language with this feature.

JQuery - File attributes

The input.files attribute is an HTML5 feature. That's why some browsers din't return anything. Simply add a fallback to the plain old input.value (string) if files doesn't exist.


How to pass arguments to a Button command in Tkinter?

The reason it invokes the method immediately and pressing the button does nothing is that action(somenumber) is evaluated and its return value is attributed as the command for the button. So if action prints something to tell you it has run and returns None, you just run action to evaluate its return value and given None as the command for the button.

To have buttons to call functions with different arguments you can use global variables, although I can't recommend it:

import Tkinter as Tk

frame = Tk.Frame(width=5, height=2, bd=1, relief=Tk.SUNKEN)
frame.pack(fill=Tk.X, padx=5, pady=5)
def action():
    global output
    global variable
button = Tk.Button(master=frame, text='press', command=action)
variable = Tk.Entry(master=frame)
output = Tk.Text(master=frame)

if __name__ == '__main__':

What I would do is make a class whose objects would contain every variable required and methods to change those as needed:

import Tkinter as Tk
class Window:
    def __init__(self):
        self.frame = Tk.Frame(width=5, height=2, bd=1, relief=Tk.SUNKEN)
        self.frame.pack(fill=Tk.X, padx=5, pady=5)

        self.button = Tk.Button(master=self.frame, text='press', command=self.action)

        self.variable = Tk.Entry(master=self.frame)

        self.output = Tk.Text(master=self.frame)

    def action(self):

if __name__ == '__main__':
    window = Window()

Keeping it simple and how to do multiple CTE in a query

You can have multiple CTEs in one query, as well as reuse a CTE:

WITH    cte1 AS
        SELECT  1 AS id
        cte2 AS
        SELECT  2 AS id
FROM    cte1
FROM    cte2
FROM    cte1

Note, however, that SQL Server may reevaluate the CTE each time it is accessed, so if you are using values like RAND(), NEWID() etc., they may change between the CTE calls.

ConfigurationManager.AppSettings - How to modify and save?

as the base question is about win forms here is the solution : ( I just changed the code by user1032413 to rflect windowsForms settings ) if it's a new key :

Configuration config = configurationManager.OpenExeConfiguration(Application.ExecutablePath); 

if the key already exists :

Configuration config = ConfigurationManager.OpenExeConfiguration(Application.ExecutablePath); 

Why is Java's SimpleDateFormat not thread-safe?

SimpleDateFormat stores intermediate results in instance fields. So if one instance is used by two threads they can mess each other's results.

Looking at the source code reveals that there is a Calendar instance field, which is used by operations on DateFormat / SimpleDateFormat.

For example parse(..) calls calendar.clear() initially and then calendar.add(..). If another thread invokes parse(..) before the completion of the first invocation, it will clear the calendar, but the other invocation will expect it to be populated with intermediate results of the calculation.

One way to reuse date formats without trading thread-safety is to put them in a ThreadLocal - some libraries do that. That's if you need to use the same format multiple times within one thread. But in case you are using a servlet container (that has a thread pool), remember to clean the thread-local after you finish.

To be honest, I don't understand why they need the instance field, but that's the way it is. You can also use joda-time DateTimeFormat which is threadsafe.

Remove NaN from pandas series

If you have a pandas serie with NaN, and want to remove it (without loosing index):

serie = serie.dropna()

# create data for example
data = np.array(['g', 'e', 'e', 'k', 's']) 
ser = pd.Series(data)
ser.replace('e', np.NAN)

0      g
1    NaN
2    NaN
3      k
4      s
dtype: object

# the code
ser = ser.dropna()

0    g
3    k
4    s
dtype: object

How can I insert a line break into a <Text> component in React Native?






HTML5 Video Autoplay not working correctly

<video width="1000px" loop="true" autoplay="autoplay" controls muted></video> worked for me

npm install private github repositories by dependency in package.json

Since Git uses curl under the hood, you can use ~/.netrc file with the credentials. For GitHub it would look something like this:

  login <github username>
  password <password OR github access token>

If you choose to use access tokens, it can be generated from:

Settings -> Developer settings -> Personal access tokens

This should also work if you are using Github Enterprise in your own corporation. just put your enterprise github url in the machine field.

Several ports (8005, 8080, 8009) required by Tomcat Server at localhost are already in use

If you are in Java EE prospective in Eclipse and trying to start the Tomcat Server in Eclipse in debug mode, then you will get such errors. You must switch to debug prospective in Eclipse. I have solved my problem like this.

jQuery detect if textarea is empty

Andy E's answer helped me get the correct way to working for me:

$.each(["input[type=text][value=]", "textarea"], function (index, element) {
if (!$(element).val() || !$(element).text()) {
 $(element).css("background-color", "rgba(255,227,3, 0.2)");

This !$(element).val() did not catch an empty textarea for me. but that whole bang (!) thing did work when combined with text.

Why does an onclick property set with setAttribute fail to work in IE?

Not relevant to the onclick issue, but also related:

For html attributes whose name collide with javascript reserved words, an alternate name is chosen, eg. <div class=''>, but div.className, or <label for='...'>, but label.htmlFor.

In reasonable browsers, this doesn't affect setAttribute. So in gecko and webkit you'd call div.setAttribute('class', 'foo'), but in IE you have to use the javascript property name instead, so div.setAttribute('className', 'foo').

MVC4 HTTP Error 403.14 - Forbidden

I solve the problem opening the visual studio, expanding the references and changing the property "Copy Local" to "True".

I discover this comparing the dlls of the old version with the Dlls of my new version (that was not working)

How to write string literals in python without having to escape them?

There is no such thing. It looks like you want something like "here documents" in Perl and the shells, but Python doesn't have that.

Using raw strings or multiline strings only means that there are fewer things to worry about. If you use a raw string then you still have to work around a terminal "\" and with any string solution you'll have to worry about the closing ", ', ''' or """ if it is included in your data.

That is, there's no way to have the string

 '   ''' """  " \

properly stored in any Python string literal without internal escaping of some sort.

filemtime "warning stat failed for"

For me the filename involved was appended with a querystring, which this function didn't like.

$path = 'path/to/my/file.js?v=2'

Solution was to chop that off first:

$path = preg_replace('/\?v=[\d]+$/', '', $path);
$fileTime = filemtime($path);

Eclipse fonts and background color

If you go to Windows, Preferences then select General, Editors, Text editors, you can set colors on that property page (and there's a link for setting MORE colors - General, Appearance, Colors and fonts).

That's with an Eclipse 3.3 build anyway.

Loading existing .html file with android WebView

paste your .html file in assets folder of your project folder. and create an xml file in layout folder with the fol code: my.xml:

<WebView  xmlns:android=""

add fol code in activity

    WebView mWebView = null;
    mWebView = (WebView) findViewById(;
    mWebView.loadUrl("file:///android_asset/new.html"); //new.html is html file name.

how to check confirm password field in form without reloading page

   <form id="form" name="form" method="post" action="registration.php" onsubmit="return check()"> 

         alert("password should be same");
         return false;

hope it may help you

MySQL error 2006: mysql server has gone away

On windows those guys using xampp should use this path xampp/mysql/bin/my.ini and change max_allowed_packet(under section[mysqld])to your choice size. e.g


Again on php.ini(xampp/php/php.ini) change upload_max_filesize the choice size. e.g


Gave me a headache for sometime till i discovered this. Hope it helps.

How to implement my very own URI scheme on Android

As the question is asked years ago, and Android is evolved a lot on this URI scheme.
From original URI scheme, to deep link, and now Android App Links.

Android now recommends to use HTTP URLs, not define your own URI scheme. Because Android App Links use HTTP URLs that link to a website domain you own, so no other app can use your links. You can check the comparison of deep link and Android App links from here

Now you can easily add a URI scheme by using Android Studio option: Tools > App Links Assistant. Please refer the detail to Android document:

Modifying the "Path to executable" of a windows service

It involves editing the registry, but service information can be found in HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services. Find the service you want to redirect, locate the ImagePath subkey and change that value.

What is the "proper" way to cast Hibernate Query.list() to List<Type>?

You use a ResultTransformer like that:

public List<Foo> activeObjects() {
    Session s = acquireSession();
    Query   q = s.createQuery("from foo where active");
    return (List<Foo>) q.list();

How to get current time and date in Android

Actually, it's safer to set the current timezone set on the device with Time.getCurrentTimezone(), or else you will get the current time in UTC.

Time today = new Time(Time.getCurrentTimezone());

Then, you can get all the date fields you want, like, for example:

textViewDay.setText(today.monthDay + "");             // Day of the month (1-31)
textViewMonth.setText(today.month + "");              // Month (0-11)
textViewYear.setText(today.year + "");                // Year 
textViewTime.setText(today.format("%k:%M:%S"));  // Current time

See android.text.format.Time class for all the details.


As many people are pointing out, Google says this class has a number of issues and is not supposed to be used anymore:

This class has a number of issues and it is recommended that GregorianCalendar is used instead.

Known issues:

For historical reasons when performing time calculations all arithmetic currently takes place using 32-bit integers. This limits the reliable time range representable from 1902 until 2037.See the wikipedia article on the Year 2038 problem for details. Do not rely on this behavior; it may change in the future. Calling switchTimezone(String) on a date that cannot exist, such as a wall time that was skipped due to a DST transition, will result in a date in 1969 (i.e. -1, or 1 second before 1st Jan 1970 UTC). Much of the formatting / parsing assumes ASCII text and is therefore not suitable for use with non-ASCII scripts.

How to find the length of an array in shell?

this works well for me

    if [ $arglen -eq '3' ];
            echo Valid Number of arguments
            echo "Arguments are $*"
            echo only four arguments are allowed

Exit single-user mode

Press CTRL + 1

find the process that locks your database. Look in column dbname for your db and note the spid. Now you have to execute that statement:

kill <your spid>

What is the correct Performance Counter to get CPU and Memory Usage of a Process?

From this post:

To get the entire PC CPU and Memory usage:

using System.Diagnostics;

Then declare globally:

private PerformanceCounter theCPUCounter = 
   new PerformanceCounter("Processor", "% Processor Time", "_Total"); 

Then to get the CPU time, simply call the NextValue() method:


This will get you the CPU usage

As for memory usage, same thing applies I believe:

private PerformanceCounter theMemCounter = 
   new PerformanceCounter("Memory", "Available MBytes");

Then to get the memory usage, simply call the NextValue() method:


For a specific process CPU and Memory usage:

private PerformanceCounter theCPUCounter = 
   new PerformanceCounter("Process", "% Processor Time",              

where Process.GetCurrentProcess().ProcessName is the process name you wish to get the information about.

private PerformanceCounter theMemCounter = 
   new PerformanceCounter("Process", "Working Set",

where Process.GetCurrentProcess().ProcessName is the process name you wish to get the information about.

Note that Working Set may not be sufficient in its own right to determine the process' memory footprint -- see What is private bytes, virtual bytes, working set?

To retrieve all Categories, see Walkthrough: Retrieving Categories and Counters

The difference between Processor\% Processor Time and Process\% Processor Time is Processor is from the PC itself and Process is per individual process. So the processor time of the processor would be usage on the PC. Processor time of a process would be the specified processes usage. For full description of category names: Performance Monitor Counters

An alternative to using the Performance Counter

Use System.Diagnostics.Process.TotalProcessorTime and System.Diagnostics.ProcessThread.TotalProcessorTime properties to calculate your processor usage as this article describes.

CSS image overlay with color and transparency

JSFiddle Demo


<div class="image-holder">
    <img src="" />


.image-holder {
    position: relative;
.image-holder:after {
    top: 0;
    left: 0;
    z-index: 10;
    width: 100%;
    height: 100%;
    display: block;
    position: absolute;
    background: blue;
    opacity: 0.1;
.image-holder:hover:after {
    opacity: 0;

AngularJS - How can I do a redirect with a full page load?

After searching and giving hit and trial session I am able to solove it by first specifying url like

$window.location.href = '/#/home/stats';

then reload


Foreach loop in java for a custom object list

for(Room room : rooms) {
  //room contains an element of rooms

JPanel Padding in Java

When you need padding inside the JPanel generally you add padding with the layout manager you are using. There are cases that you can just expand the border of the JPanel.

Create text file and fill it using bash

if [ -e $policy ]; then
  echo "File $1.json already exists!"
  cat > $file_location <<EOF
      "contact": {
          "name": "xyz",
          "phonenumber":   "xxx-xxx-xxxx"

This code checks if the given JSON file of the user is present in test home directory or not. If it's not present it will create it with the content. You can modify the file location and content according to your needs.

What is a magic number, and why is it bad?

It is worth noting that sometimes you do want non-configurable "hard-coded" numbers in your code. There are a number of famous ones including 0x5F3759DF which is used in the optimized inverse square root algorithm.

In the rare cases where I find the need to use such Magic Numbers, I set them as a const in my code, and document why they are used, how they work, and where they came from.

node.js Error: connect ECONNREFUSED; response from server

From your code, It looks like your file contains code that makes get request to localhost (

The problem might be you have not created server on your local machine which listens to port 8000.

For that you have to set up server on localhost which can serve your request.

  1. Create server.js

    var express = require('express');
    var app = express();
    app.get('/', function (req, res) {
      res.send('Hello World!'); // This will serve your request to '/'.
    app.listen(8000, function () {
      console.log('Example app listening on port 8000!');
  2. Run server.js : node server.js

  3. Run file that contains code to make request.

How to fix 'android.os.NetworkOnMainThreadException'?

This is only thrown for applications targeting the Honeycomb SDK or higher. Applications targeting earlier SDK versions are allowed to do networking on their main event loop threads.

The error is the SDK warning!

Apply CSS style attribute dynamically in Angular JS

The easiest way is to call a function for the style, and have the function return the correct style.

<div style="{{functionThatReturnsStyle()}}"></div>

And in your controller:

$scope.functionThatReturnsStyle = function() {
  var style1 = "width: 300px";
  var style2 = "width: 200px";
     return style1;
     return style2;

modal View controllers - how to display and dismiss

I think you misunderstood some core concepts about iOS modal view controllers. When you dismiss VC1, any presented view controllers by VC1 are dismissed as well. Apple intended for modal view controllers to flow in a stacked manner - in your case VC2 is presented by VC1. You are dismissing VC1 as soon as you present VC2 from VC1 so it is a total mess. To achieve what you want, buttonPressedFromVC1 should have the mainVC present VC2 immediately after VC1 dismisses itself. And I think this can be achieved without delegates. Something along the lines:

UIViewController presentingVC = [self presentingViewController];
[self dismissViewControllerAnimated:YES completion:
    [presentingVC presentViewController:vc2 animated:YES completion:nil];

Note that self.presentingViewController is stored in some other variable, because after vc1 dismisses itself, you shouldn't make any references to it.

How to serve an image using nodejs

Vanilla node version as requested:

var http = require('http');
var url = require('url');
var path = require('path');
var fs = require('fs');

http.createServer(function(req, res) {
  // parse url
  var request = url.parse(req.url, true);
  var action = request.pathname;
  // disallow non get requests
  if (req.method !== 'GET') {
    res.writeHead(405, {'Content-Type': 'text/plain' });
    res.end('405 Method Not Allowed');
  // routes
  if (action === '/') {
    res.writeHead(200, {'Content-Type': 'text/plain' });
    res.end('Hello World \n');
  // static (note not safe, use a module for anything serious)
  var filePath = path.join(__dirname, action).split('%20').join(' ');
  fs.exists(filePath, function (exists) {
    if (!exists) {
       // 404 missing files
       res.writeHead(404, {'Content-Type': 'text/plain' });
       res.end('404 Not Found');
    // set the content type
    var ext = path.extname(action);
    var contentType = 'text/plain';
    if (ext === '.gif') {
       contentType = 'image/gif'
    res.writeHead(200, {'Content-Type': contentType });
    // stream the file
    fs.createReadStream(filePath, 'utf-8').pipe(res);
}).listen(8080, '');

How to debug Lock wait timeout exceeded on MySQL?

What gives this away is the word transaction. It is evident by the statement that the query was attempting to change at least one row in one or more InnoDB tables.

Since you know the query, all the tables being accessed are candidates for being the culprit.

From there, you should be able to run SHOW ENGINE INNODB STATUS\G

You should be able to see the affected table(s)

You get all kinds of additional Locking and Mutex Information.

Here is a sample from one of my clients:

mysql> show engine innodb status\G
*************************** 1. row ***************************
  Type: InnoDB
Per second averages calculated from the last 4 seconds
OS WAIT ARRAY INFO: reservation count 9014315, signal count 7805377
Mutex spin waits 0, rounds 11487096053, OS waits 7756855
RW-shared spins 722142, OS waits 211221; RW-excl spins 787046, OS waits 39353
110507 21:41:35 Transaction:
TRANSACTION 0 606162814, ACTIVE 0 sec, process no 29956, OS thread id 1223895360 updating or deleting, thread declared inside InnoDB 499
mysql tables in use 1, locked 1
14 lock struct(s), heap size 3024, 8 row lock(s), undo log entries 1
MySQL thread id 3686635, query id 124164167 viget updating
DELETE FROM file WHERE file_id in ('6dbafa39-7f00-0001-51f2-412a450be5cc' )
Foreign key constraint fails for table `backoffice`.`attachment`:
  CONSTRAINT `attachment_ibfk_2` FOREIGN KEY (`file_id`) REFERENCES `file` (`file_id`)
Trying to delete or update in parent table, in index `PRIMARY` tuple:
DATA TUPLE: 17 fields;
 0: len 36; hex 36646261666133392d376630302d303030312d353166322d343132613435306265356363; asc 6dbafa39-7f00-0001-51f2-412a450be5cc;; 1: len 6; hex 000024214f7e; asc   $!O~;; 2: len 7; hex 000000400217bc; asc    @   ;; 3: len 2; hex 03e9; asc   ;; 4: len 2; hex 03e8; asc   ;; 5: len 36; hex 65666635323863622d376630302d303030312d336632662d353239626433653361333032; asc eff528cb-7f00-0001-3f2f-529bd3e3a302;; 6: len 40; hex 36646234376337652d376630302d303030312d353166322d3431326132346664656366352e6d7033; asc 6db47c7e-7f00-0001-51f2-412a24fdecf5.mp3;; 7: len 21; hex 416e67656c73204e6f7720436f6e666572656e6365; asc Angels Now Conference;; 8: len 34; hex 416e67656c73204e6f7720436f6e666572656e6365204a756c7920392c2032303131; asc Angels Now Conference July 9, 2011;; 9: len 1; hex 80; asc  ;; 10: len 8; hex 8000124a5262bdf4; asc    JRb  ;; 11: len 8; hex 8000124a57669dc3; asc    JWf  ;; 12: SQL NULL; 13: len 5; hex 8000012200; asc    " ;; 14: len 1; hex 80; asc  ;; 15: len 2; hex 83e8; asc   ;; 16: len 4; hex 8000000a; asc     ;;

But in child table `backoffice`.`attachment`, in index `PRIMARY`, there is a record:
PHYSICAL RECORD: n_fields 6; compact format; info bits 0
 0: len 30; hex 36646261666133392d376630302d303030312d353166322d343132613435; asc 6dbafa39-7f00-0001-51f2-412a45;...(truncated); 1: len 30; hex 38666164663561652d376630302d303030312d326436612d636164326361; asc 8fadf5ae-7f00-0001-2d6a-cad2ca;...(truncated); 2: len 6; hex 00002297b3ff; asc   "   ;; 3: len 7; hex 80000040070110; asc    @   ;; 4: len 2; hex 0000; asc   ;; 5: len 30; hex 416e67656c73204e6f7720436f6e666572656e636520446f63756d656e74; asc Angels Now Conference Document;;

Trx id counter 0 620783814
Purge done for trx's n:o < 0 620783800 undo n:o < 0 0
History list length 35
---TRANSACTION 0 0, not started, process no 29956, OS thread id 1192212800
MySQL thread id 5341758, query id 189708501 lwdba
show innodb status
---TRANSACTION 0 620783788, not started, process no 29956, OS thread id 1196472640
MySQL thread id 5341773, query id 189708353 viget
---TRANSACTION 0 0, not started, process no 29956, OS thread id 1223895360
MySQL thread id 5341667, query id 189706152 viget
---TRANSACTION 0 0, not started, process no 29956, OS thread id 1227888960
MySQL thread id 5341556, query id 189699857 lwdba
---TRANSACTION 0 620781112, not started, process no 29956, OS thread id 1222297920
MySQL thread id 5341511, query id 189696265 viget
---TRANSACTION 0 620783736, not started, process no 29956, OS thread id 1229752640
MySQL thread id 5339005, query id 189707998 viget
---TRANSACTION 0 620783785, not started, process no 29956, OS thread id 1198602560
MySQL thread id 5337583, query id 189708349 viget
---TRANSACTION 0 620783469, not started, process no 29956, OS thread id 1224161600
MySQL thread id 5333500, query id 189708478 viget
---TRANSACTION 0 620781240, not started, process no 29956, OS thread id 1198336320
MySQL thread id 5324256, query id 189708493 viget
---TRANSACTION 0 617458223, not started, process no 29956, OS thread id 1195141440
MySQL thread id 736, query id 175038790 Has read all relay log; waiting for the slave I/O thread to update it
I/O thread 0 state: waiting for i/o request (insert buffer thread)
I/O thread 1 state: waiting for i/o request (log thread)
I/O thread 2 state: waiting for i/o request (read thread)
I/O thread 3 state: waiting for i/o request (write thread)
Pending normal aio reads: 0, aio writes: 0,
 ibuf aio reads: 0, log i/o's: 0, sync i/o's: 0
Pending flushes (fsync) log: 0; buffer pool: 0
519878 OS file reads, 18962880 OS file writes, 13349046 OS fsyncs
0.00 reads/s, 0 avg bytes/read, 6.25 writes/s, 4.50 fsyncs/s
Ibuf: size 1, free list len 1190, seg size 1192,
174800 inserts, 174800 merged recs, 54439 merges
Hash table size 35401603, node heap has 35160 buffer(s)
0.50 hash searches/s, 11.75 non-hash searches/s
Log sequence number 28 1235093534
Log flushed up to   28 1235093534
Last checkpoint at  28 1235091275
0 pending log writes, 0 pending chkp writes
12262564 log i/o's done, 3.25 log i/o's/second
Total memory allocated 18909316674; in additional pool allocated 1048576
Dictionary memory allocated 2019632
Buffer pool size   1048576
Free buffers       175763
Database pages     837653
Modified db pages  6
Pending reads 0
Pending writes: LRU 0, flush list 0, single page 0
Pages read 770138, created 108485, written 7795318
0.00 reads/s, 0.00 creates/s, 4.25 writes/s
Buffer pool hit rate 1000 / 1000
0 queries inside InnoDB, 0 queries in queue
1 read views open inside InnoDB
Main thread process no. 29956, id 1185823040, state: sleeping
Number of rows inserted 6453767, updated 4602534, deleted 3638793, read 388349505551
0.25 inserts/s, 1.25 updates/s, 0.00 deletes/s, 2.75 reads/s

1 row in set, 1 warning (0.00 sec)

You should consider increasing the lock wait timeout value for InnoDB by setting the innodb_lock_wait_timeout, default is 50 sec

mysql> show variables like 'innodb_lock_wait_timeout';
| Variable_name            | Value |
| innodb_lock_wait_timeout | 50    |
1 row in set (0.01 sec)

You can set it to higher value in /etc/my.cnf permanently with this line


and restart mysql. If you cannot restart mysql at this time, run this:

SET GLOBAL innodb_lock_wait_timeout = 120; 

You could also just set it for the duration of your session

SET innodb_lock_wait_timeout = 120; 

followed by your query

Equivalent of typedef in C#

C# supports some inherited covariance for event delegates, so a method like this:

void LowestCommonHander( object sender, EventArgs e ) { ... } 

Can be used to subscribe to your event, no explicit cast required

gcInt.MyEvent += LowestCommonHander;

You can even use lambda syntax and the intellisense will all be done for you:

gcInt.MyEvent += (sender, e) =>
    e. //you'll get correct intellisense here

std::wstring VS std::string

1) As mentioned by Greg, wstring is helpful for internationalization, that's when you will be releasing your product in languages other than english

4) Check this out for wide character

How to add a boolean datatype column to an existing table in sql?

In SQL SERVER it is BIT, though it allows NULL to be stored

ALTER TABLE person add  [AdminApproved] BIT default 'FALSE';

Also there are other mistakes in your query

  1. When you alter a table to add column no need to mention column keyword in alter statement

  2. For adding default constraint no need to use SET keyword

  3. Default value for a BIT column can be ('TRUE' or '1') / ('FALSE' or 0). TRUE or FALSE needs to mentioned as string not as Identifier

How to get input type using jquery?

You could do the following:

var inputType = $('#inputid').attr('type');

PHP replacing special characters like à->a, è->e

CodeIgniter way:


$string = convert_accented_characters($string);

This function uses a companion config file application/config/foreign_chars.php to define the to and from array for transliteration.

Using array map to filter results with if conditional

Here's some info if someone comes upon this in 2019.

I think reduce vs map + filter might be somewhat dependent on what you need to loop through. Not sure on this but reduce does seem to be slower.

One thing is for sure - if you're looking for performance improvements the way you write the code is extremely important!

Here a JS perf test that shows the massive improvements when typing out the code fully rather than checking for "falsey" values (e.g. if (string) {...}) or returning "falsey" values where a boolean is expected.

Hope this helps someone

What is the opposite of :hover (on mouse leave)?

Put your duration time in the non-hover selection:

li a {
  background-color: #111;

li a:hover {

Difference between Select Unique and Select Distinct

Unique is a keyword used in the Create Table() directive to denote that a field will contain unique data, usually used for natural keys, foreign keys etc.

For example:

Create Table Employee(   
    Emp_PKey Int Identity(1, 1) Constraint PK_Employee_Emp_PKey Primary Key,  
    Emp_SSN Numeric Not Null Unique,  
    Emp_FName varchar(16),   
    Emp_LName varchar(16) 

i.e. Someone's Social Security Number would likely be a unique field in your table, but not necessarily the primary key.

Distinct is used in the Select statement to notify the query that you only want the unique items returned when a field holds data that may not be unique.

Select Distinct Emp_LName
From Employee

You may have many employees with the same last name, but you only want each different last name.

Obviously if the field you are querying holds unique data, then the Distinct keyword becomes superfluous.

Redirect stderr to stdout in C shell

What about just

xxx >& /dev/stdout


"Register" an .exe so you can run it from any command line in Windows

It is very simple and it won't take more than 30 seconds.

For example the software called abc located in D:/Softwares/vlc/abc.exe Add the folder path of abc.exe to system environment variables.

My Computer -> Click Properties -> Click Advanced system settings -> Click Environment Variables

enter image description here

enter image description here

Click on Ok.

now you can just open cmd prompt and you can launch the software from anywhere. to use abc.exe just type abc in the command line.

How do I detect whether 32-bit Java is installed on x64 Windows, only looking at the filesystem and registry?

Do you have access to the command prompt ?

Method 1 : Command Prompt

The specifics of the Java installed on the system can be determined by executing the following command java -version

Method 2 : Folder Structure

In case you do not have access to command prompt then determining the folder where Java.

32 Bit : C:\Program Files (x86)\Java\jdk1.6.0_30

64 Bit : C:\Program Files\Java\jdk1.6.0_25

However during the installation it is possible that the user might change the installation folder.

Method 3 : Registry

You can also see the version installed in registry editor.

  1. Go to registry editor

  2. Edit -> Find

  3. Search for Java. You will get the registry entries for Java.

  4. In the entry with name : DisplayName & DisplayVersion, the installed java version is displayed

How can I run another application within a panel of my C# program?

Using the win32 API it is possible to "eat" another application. Basically you get the top window for that application and set it's parent to be the handle of the panel you want to place it in. If you don't want the MDI style effect you also have to adjust the window style to make it maximised and remove the title bar.

Here is some simple sample code where I have a form with a button and a panel:

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.Diagnostics;
using System.Runtime.InteropServices;
using System.Threading;

namespace WindowsFormsApplication2
    public partial class Form1 : Form
        public Form1()

        private void button1_Click(object sender, EventArgs e)
            Process p = Process.Start("notepad.exe");
            Thread.Sleep(500); // Allow the process to open it's window
            SetParent(p.MainWindowHandle, panel1.Handle);

        static extern IntPtr SetParent(IntPtr hWndChild, IntPtr hWndNewParent);

I just saw another example where they called WaitForInputIdle instead of sleeping. So the code would be like this:

Process p = Process.Start("notepad.exe");
SetParent(p.MainWindowHandle, panel1.Handle);

The Code Project has a good article one the whole process: Hosting EXE Applications in a WinForm project

react-native - Fit Image in containing View, not the whole screen size

I think it's because you didn't specify the width and height for the item.

If you only want to have 2 images in a row, you can try something like this instead of using flex:

item: {
    width: '50%',
    height: '100%',
    overflow: 'hidden',
    alignItems: 'center',
    backgroundColor: 'orange',
    position: 'relative',
    margin: 10,

This works for me, hope it helps.

"No cached version... available for offline mode."

Had the same error after updating Android Studio today. For me, it wasn't a matter of proxy settings:

  1. Uncheck "Offline work" in Android Studio 0.6.0:

    File->Settings->Gradle->Global Gradle Settings

    or in OSX:

    Preferences->Gradle->Global Gradle Setting

    or in more recent versions:

    File->Settings->Build, Execution, Deployment->Build tools->Gradle

  2. Resync the project, for example by restarting the Android Studio

  3. Once synced, you can check the option again to work offline.

(Only tested in Gradle version 0.11... and Android Studio version 0.6.0 Preview)

EDIT : Added paths for different versions/platforms (as mentioned by John Ballinger and The_Martian). Not yet verified.

Returning IEnumerable<T> vs. IQueryable<T>

I would like to clarify a few things due to seemingly conflicting responses (mostly surrounding IEnumerable).

(1) IQueryable extends the IEnumerable interface. (You can send an IQueryable to something which expects IEnumerable without error.)

(2) Both IQueryable and IEnumerable LINQ attempt lazy loading when iterating over the result set. (Note that implementation can be seen in interface extension methods for each type.)

In other words, IEnumerables are not exclusively "in-memory". IQueryables are not always executed on the database. IEnumerable must load things into memory (once retrieved, possibly lazily) because it has no abstract data provider. IQueryables rely on an abstract provider (like LINQ-to-SQL), although this could also be the .NET in-memory provider.

Sample use case

(a) Retrieve list of records as IQueryable from EF context. (No records are in-memory.)

(b) Pass the IQueryable to a view whose model is IEnumerable. (Valid. IQueryable extends IEnumerable.)

(c) Iterate over and access the data set's records, child entities and properties from the view. (May cause exceptions!)

Possible Issues

(1) The IEnumerable attempts lazy loading and your data context is expired. Exception thrown because provider is no longer available.

(2) Entity Framework entity proxies are enabled (the default), and you attempt to access a related (virtual) object with an expired data context. Same as (1).

(3) Multiple Active Result Sets (MARS). If you are iterating over the IEnumerable in a foreach( var record in resultSet ) block and simultaneously attempt to access record.childEntity.childProperty, you may end up with MARS due to lazy loading of both the data set and the relational entity. This will cause an exception if it is not enabled in your connection string.


  • I have found that enabling MARS in the connection string works unreliably. I suggest you avoid MARS unless it is well-understood and explicitly desired.

Execute the query and store results by invoking resultList = resultSet.ToList() This seems to be the most straightforward way of ensuring your entities are in-memory.

In cases where the you are accessing related entities, you may still require a data context. Either that, or you can disable entity proxies and explicitly Include related entities from your DbSet.

Format an Integer using Java String Format

String.format("%03d", 1)  // => "001"
//              ¦¦¦   +-- print the number one
//              ¦¦+------ ... as a decimal integer
//              ¦+------- ... minimum of 3 characters wide
//              +-------- ... pad with zeroes instead of spaces

See java.util.Formatter for more information.

How to use Apple's new San Francisco font on a webpage

You can not use Apple System Font served directly from a database. It's against the License, but you can use this for Mac Systems higher than High Sierra

  font-family: -apple-system, "Helvetica Neue", "Lucida Grande";

Or you can use this:

font-family: 'BlinkMacSystemFont';

How can I change the language (to english) in Oracle SQL Developer?

Before installation use the Control Panel Region and Language Preferences tool to change everything (Format, Keyboard default input, language for non Unicode programs) to English. Revert to the original selections after the installation.

Subset and ggplot2

@agstudy's answer didn't work for me with the latest version of ggplot2, but this did, using maggritr pipes:

  geom_line(aes(Value1, Value2, group=ID, colour=ID),
                data = . %>% filter(ID %in% c("P1" , "P3")))

It works because if geom_line sees that data is a function, it will call that function with the inherited version of data and use the output of that function as data.

Applying a single font to an entire website with CSS

As a different font is likely to be already defined by the browser for form elements, here are 2 ways to use this font everywhere:

body, input, textarea {
    font-family: Algerian;

body {
    font-family: Algerian !important;

There'll still have a monospace font on elements like pre/code, kbd, etc but, in case you use these elements, you'd better use a monospace font there.

Important note: if very few people has this font installed on their OS, then the second font in the list will be used. Here you defined no second font so the default serif font will be used, and it'll be Times, Times New Roman except maybe on Linux.
Two options there: use @font-face if your font is free of use as a downloadable font or add fallback(s): a second, a third, etc and finally a default family (sans-serif, cursive (*), monospace or serif). The first of the list that exists on the OS of the user will be used.

(*) default cursive on Windows is Comic Sans. Except if you want to troll Windows users, don't do that :) This font is terrible except for your children birthdays where it's welcome.

What is the difference between hg forget and hg remove?

A file can be tracked or not, you use hg add to track a file and hg remove or hg forget to un-track it. Using hg remove without flags will both delete the file and un-track it, hg forget will simply un-track it without deleting it.

How to determine the content size of a UIWebView?

This's weird!

I tested the solutions both sizeThatFits: and [webView stringByEvaluatingJavaScriptFromString:@"document.body.scrollHeight"] are NOT working for me.

However, I found an interesting easy way to get the right height of webpage content. Currently, I used it in my delegate method scrollViewDidScroll:.

CGFloat contentHeight = scrollView.contentSize.height - CGRectGetHeight(scrollView.frame);

Verified in iOS 9.3 Simulator/Device, good luck!


Background: The html content is calculated by my string variable and HTTP content template, loaded by method loadHTMLString:baseURL:, no registered JS scripts there.

Forward slash in Java Regex

Double escaping is required when presented as a string.

Whenever I'm making a new regular expression I do a bunch of tests with online tools, for example:

That website allows you to enter the regular expression, which it'll escape into a string for you, and you can then test it against different inputs.

Get a list of all functions and procedures in an Oracle database


The column STATUS tells you whether the object is VALID or INVALID. If it is invalid, you have to try a recompile, ORACLE can't tell you if it will work before.

program cant start because php5.dll is missing

For Wamp x86+Phalcon users (with same error):

Take care of download the right version of Phalcon:

Phalcon 1.3.2 - Windows x86 for PHP 5.5.0 (VC11)

docker entrypoint running bash script gets "permission denied"

If you still get Permission denied errors when you try to run your script in the docker's entrypoint, just try DO NOT use the shell form of the entrypoint:

Instead of: ENTRYPOINT ./bin/watcher write ENTRYPOINT ["./bin/watcher"]:

enter image description here

window.history.pushState refreshing the browser

As others have suggested, you are not clearly explaining your problem, what you are trying to do, or what your expectations are as to what this function is actually supposed to do.

If I have understood correctly, then you are expecting this function to refresh the page for you (you actually use the term "reloads the browser").

But this function is not intended to reload the browser.

All the function does, is to add (push) a new "state" onto the browser history, so that in future, the user will be able to return to this state that the web-page is now in.

Normally, this is used in conjunction with AJAX calls (which refresh only a part of the page).

For example, if a user does a search "CATS" in one of your search boxes, and the results of the search (presumably cute pictures of cats) are loaded back via AJAX, into the lower-right of your page -- then your page state will not be changed. In other words, in the near future, when the user decides that he wants to go back to his search for "CATS", he won't be able to, because the state doesn't exist in his history. He will only be able to click back to your blank search box.

Hence the need for the function

history.pushState({},"Results for `Cats`",'url.html?s=cats');

It is intended as a way to allow the programmer to specifically define his search into the user's history trail. That's all it is intended to do.

When the function is working properly, the only thing you should expect to see, is the address in your browser's address-bar change to whatever you specify in your URL.

If you already understand this, then sorry for this long preamble. But it sounds from the way you pose the question, that you have not.

As an aside, I have also found some contradictions between the way that the function is described in the documentation, and the way it works in reality. I find that it is not a good idea to use blank or empty values as parameters.

See my answer to this SO question. So I would recommend putting a description in your second parameter. From memory, this is the description that the user sees in the drop-down, when he clicks-and-holds his mouse over "back" button.

How to convert MySQL time to UNIX timestamp using PHP?

Use strtotime(..):

$timestamp = strtotime($mysqltime);
echo date("Y-m-d H:i:s", $timestamp);

Also check this out (to do it in MySQL way.)

Import CSV into SQL Server (including automatic table creation)

You can create a temp table variable and insert the data into it, then insert the data into your actual table by selecting it from the temp table.

 declare @TableVar table 
    firstCol varchar(50) NOT NULL,
    secondCol varchar(50) NOT NULL


INSERT INTO dbo.ExistingTable
SELECT firstCol,
FROM @TableVar


Angular2 dynamic change CSS property

I did this plunker to explore one way to do what you want.

Here I get mystyle from the parent component but you can get it from a service.

import {Component, View} from 'angular2/angular2'

  selector: '[my-person]',
  inputs: [
    'mystyle: customstyle'
  host: {
    '[style.backgroundColor]': 'mystyle.backgroundColor'
  template: `My Person Component: {{ name }}`
export class Person {}

Rebuild all indexes in a Database

Daniel's script appears to be a good all encompassing solution, but even he admitted that his laptop ran out of memory. Here is an option I came up with. I based my procedure off of Mohammad Nizamuddin's post on TechNet. I added an initial cursor loop that pulls all the database names into a temporary table and then uses that to pull all the base table names from each of those databases.

You can optionally pass the fill factor you would prefer and specify a target database if you do not want to re-index all databases.

-- Name:  sp_RebuildAllIndexes
-- Arguements:  [Fill Factor], [Target Database name]
-- Purpose:  Loop through all the databases on a server and
--           compile a list of all the table within them.
--           This list is then used to rebuild indexes for
--           all the tables in all the database.  Optionally,
--           you may pass a specific database name if you only
--           want to reindex that target database.
CREATE PROCEDURE sp_RebuildAllIndexes(
    @FillFactor     INT = 90,
    @TargetDatabase NVARCHAR(100) = NULL)
        DECLARE @TablesToReIndex TABLE (
            TableName VARCHAR(200)
        DECLARE @DbName VARCHAR(50);
        DECLARE @TableSelect VARCHAR(MAX);
        DECLARE @DatabasesToIndex CURSOR;

        IF ISNULL( @TargetDatabase, '' ) = ''
          SET @DatabasesToIndex = CURSOR
              FROM   master..sysdatabases
          SET @DatabasesToIndex = CURSOR
              FROM   master..sysdatabases
              WHERE  NAME = @TargetDatabase

        OPEN DatabasesToIndex

        FETCH NEXT FROM DatabasesToIndex INTO @DbName

        WHILE @@FETCH_STATUS = 0
                SET @TableSelect = 'INSERT INTO @TablesToReIndex SELECT CONCAT(TABLE_CATALOG, ''.'', TABLE_SCHEMA, ''.'', TABLE_NAME) AS TableName FROM '
                                   + @DbName
                                   + '.INFORMATION_SCHEMA.TABLES WHERE TABLE_TYPE = ''base table''';

                EXEC sp_executesql

                FETCH NEXT FROM DatabasesToIndex INTO @DbName

        CLOSE DatabasesToIndex

        DEALLOCATE DatabasesToIndex

        DECLARE @TableName VARCHAR(255)
        DECLARE TableCursor CURSOR FOR
            SELECT TableName
            FROM   @TablesToReIndex

        OPEN TableCursor

        FETCH NEXT FROM TableCursor INTO @TableName

        WHILE @@FETCH_STATUS = 0
                DBCC DBREINDEX(@TableName, ' ', @FillFactor)

                FETCH NEXT FROM TableCursor INTO @TableName

        CLOSE TableCursor

        DEALLOCATE TableCursor

How can I find the first and last date in a month using PHP?

For specific month and year use date() as natural language as following

$first_date = date('d-m-Y',strtotime('first day of april 2010'));
$last_date = date('d-m-Y',strtotime('last day of april 2010'));
// Isn't it simple way?

but for Current month

$first_date = date('d-m-Y',strtotime('first day of this month'));
$last_date = date('d-m-Y',strtotime('last day of this month'));

Rails: select unique values from a column

The result of this is a collection of Model objects. Not plain ratings. And from uniq's point of view, they are completely different. You can use this:

or this (most efficient):


Rails 5+



Apparently, as of rails, it works only on "top level" queries, like above. Doesn't work on collection proxies ("has_many" relations, for example).

Address.distinct.pluck(:city) # => ['Moscow']
user.addresses.distinct.pluck(:city) # => ['Moscow', 'Moscow', 'Moscow']

In this case, deduplicate after the query

user.addresses.pluck(:city).uniq # => ['Moscow']

Google reCAPTCHA: How to get user response and validate in the server side?

Here is complete demo code to understand client side and server side process. you can copy paste it and just replace google site key and google secret key.

      //  echo '<pre>'; print_r($_REQUEST); die('END');
        $post = [
            'secret' => 'Your Secret key',
            'response' => $_REQUEST['g-recaptcha-response'],
        $ch = curl_init();

        curl_setopt($ch, CURLOPT_URL,"");
        curl_setopt($ch, CURLOPT_POST, 1);
        curl_setopt($ch, CURLOPT_POSTFIELDS, http_build_query($post));
        curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);

        $server_output = curl_exec($ch);

        curl_close ($ch);
        echo '<pre>'; print_r($server_output); die('ss');
    <title>reCAPTCHA demo: Explicit render for multiple widgets</title>
    <script type="text/javascript">
      var site_key = 'Your Site key';
      var verifyCallback = function(response) {
      var widgetId1;
      var widgetId2;
      var onloadCallback = function() {
        // Renders the HTML element with id 'example1' as a reCAPTCHA widget.
        // The id of the reCAPTCHA widget is assigned to 'widgetId1'.
        widgetId1 = grecaptcha.render('example1', {
          'sitekey' : site_key,
          'theme' : 'light'
        widgetId2 = grecaptcha.render(document.getElementById('example2'), {
          'sitekey' : site_key
        grecaptcha.render('example3', {
          'sitekey' : site_key,
          'callback' : verifyCallback,
          'theme' : 'dark'
    <!-- The g-recaptcha-response string displays in an alert message upon submit. -->
    <form action="javascript:alert(grecaptcha.getResponse(widgetId1));">
      <div id="example1"></div>
      <input type="submit" value="getResponse">
    <!-- Resets reCAPTCHA widgetId2 upon submit. -->
    <form action="javascript:grecaptcha.reset(widgetId2);">
      <div id="example2"></div>
      <input type="submit" value="reset">
    <!-- POSTs back to the page's URL upon submit with a g-recaptcha-response POST parameter. -->
    <form action="?" method="POST">
      <div id="example3"></div>
      <input type="submit" value="Submit">
    <script src=""
        async defer>

How to ignore the first line of data when processing CSV data?

use csv.DictReader instead of csv.Reader. If the fieldnames parameter is omitted, the values in the first row of the csvfile will be used as field names. you would then be able to access field values using row["1"] etc

php create object without class

you can always use new stdClass(). Example code:

   $object = new stdClass();
   $object->property = 'Here we go';


   object(stdClass)#2 (1) {
      string(10) "Here we go"

Also as of PHP 5.4 you can get same output with:

$object = (object) ['property' => 'Here we go'];

Print Currency Number Format in PHP

sprintf() is the PHP function for all sorts of string formatting

I use this function:

function formatDollars($dollars){
  return '$ '.sprintf('%0.2f', $dollars);

How to recursively find and list the latest modified files in a directory with subdirectories and times

Both the Perl and Python solutions in this post helped me solve this problem on Mac OS X:

How to list files sorted by modification date recursively (no stat command available!)

Quoting from the post:


find . -type f -print |
perl -l -ne '
    $_{$_} = -M;  # store file age (mtime - now)
    END {
        print sort {$_{$b} <=> $_{$a}} keys %_;  # print by decreasing age


find . -type f -print |
python -c 'import os, sys; times = {}
for f in sys.stdin.readlines(): f = f[0:-1]; times[f] = os.stat(f).st_mtime
for f in sorted(times.iterkeys(), key=lambda f:times[f]): print f'

Set icon for Android application

  1. Choose icon picture copy this pic
  2. Paste it into your project's res/drawable folder
  3. Open manifest file and set

  4. Run program

How to populate a sub-document in mongoose after creating it?

This might have changed since the original answer was written, but it looks like you can now use the Models populate function to do this without having to execute an extra findOne. See: You'd want to use this inside the save handler just like the findOne is.

Using CSS how to change only the 2nd column of a table

You could designate a class for each cell in the second column.

<tr><td>Column 1</td><td class="col2">Col 2</td></tr>
<tr><td>Column 1</td><td class="col2">Col 2</td></tr>
<tr><td>Column 1</td><td class="col2">Col 2</td></tr>
<tr><td>Column 1</td><td class="col2">Col 2</td></tr>

How to store directory files listing into an array?

Here's a variant that lets you use a regex pattern for initial filtering, change the regex to be get the filtering you desire.

files=($(find -E . -type f -regex "^.*$"))
for item in ${files[*]}
  printf "   %s\n" $item

Why does checking a variable against multiple values with `OR` only check the first value?

if name in ("Jesse", "jesse"):

would be the correct way to do it.

Although, if you want to use or, the statement would be

if name == 'Jesse' or name == 'jesse':

>>> ("Jesse" or "jesse")

evaluates to 'Jesse', so you're essentially not testing for 'jesse' when you do if name == ("Jesse" or "jesse"), since it only tests for equality to 'Jesse' and does not test for 'jesse', as you observed.

How to pass arguments to addEventListener listener function?

There is absolutely nothing wrong with the code you've written. Both some_function and someVar should be accessible, in case they were available in the context where anonymous

function() { some_function(someVar); } 

was created.

Check if the alert gives you the value you've been looking for, be sure it will be accessible in the scope of anonymous function (unless you have more code that operates on the same someVar variable next to the call to addEventListener)

var someVar; 
someVar = some_other_function();
someObj.addEventListener("click", function(){
}, false);

How to resolve 'npm should be run outside of the node repl, in your normal shell'

Do not run the application using node.js icon.

Go to All Programmes->Node.js->Node.js command prompt.

Below is example screen shot.

enter image description here

enter image description here

Excel VBA Run-time error '13' Type mismatch


Justin has given you some very fine tips :)

You will also get that error if the cell where you are performing the calculation has an error resulting from a formula.

For example if Cell A1 has #DIV/0! error then you will get "Excel VBA Run-time error '13' Type mismatch" when performing this code

Sheets("Sheet1").Range("A1").Value - 1

I have made some slight changes to your code. Could you please test it for me? Copy the code with the line numbers as I have deliberately put them there.

Option Explicit

Sub Sample()
  Dim ws As Worksheet
  Dim x As Integer, i As Integer, a As Integer, y As Integer
  Dim name As String
  Dim lastRow As Long
10        On Error GoTo Whoa

20        Application.ScreenUpdating = False

30        name = InputBox("Please insert the name of the sheet")

40        If Len(Trim(name)) = 0 Then Exit Sub

50        Set ws = Sheets(name)

60        With ws
70            If Not IsError(.Range("BE4").Value) Then
80                x = Val(.Range("BE4").Value)
90            Else
100               MsgBox "Please check the value of cell BE4. It seems to have an error"
110               GoTo LetsContinue
120           End If

130           .Range("BF4").Value = x

140           lastRow = .Range("BE" & Rows.Count).End(xlUp).Row

150           For i = 5 To lastRow
160               If IsError(.Range("BE" & i)) Then
170                   MsgBox "Please check the value of cell BE" & i & ". It seems to have an error"
180                   GoTo LetsContinue
190               End If

200               a = 0: y = Val(.Range("BE" & i))
210               If y <> x Then
220                   If y <> 0 Then
230                       If y = 3 Then
240                           a = x
250                           .Range("BF" & i) = Val(.Range("BE" & i)) - x

260                           x = Val(.Range("BE" & i)) - x
270                       End If
280                       .Range("BF" & i) = Val(.Range("BE" & i)) - a
290                       x = Val(.Range("BE" & i)) - a
300                   Else
310                       .Range("BF" & i).ClearContents
320                   End If
330               Else
340                   .Range("BF" & i).ClearContents
350               End If
360           Next i
370       End With

380       Application.ScreenUpdating = True
390       Exit Sub
400       MsgBox "Error Description :" & Err.Description & vbNewLine & _
         "Error at line     : " & Erl
410       Resume LetsContinue
End Sub

How to find the socket connection state in C?

For BSD sockets I'd check out Beej's guide. When recv returns 0 you know the other side disconnected.

Now you might actually be asking, what is the easiest way to detect the other side disconnecting? One way of doing it is to have a thread always doing a recv. That thread will be able to instantly tell when the client disconnects.

The operation couldn’t be completed. (com.facebook.sdk error 2.) ios6

I had the same issue and took a whole day to figure out the problem. This error message by Facebook SDK is very vague. I had this problem due to openURL: method being overwritten in MyApplication. I removed the overwritten method and facebook login worked fine.

Return JSON with error status code MVC

A simple way to send a error to Json is control Http Status Code of response object and set a custom error message.


public JsonResult Create(MyObject myObject) 
  return Json(new { IsCreated = True, Content = ViewGenerator(myObject));

  //Use input may be wrong but nothing crashed
  return Json(new { IsCreated = False, Content = ViewGenerator(myObject));  

  Response.StatusCode = (int)HttpStatusCode.InternalServerError;
  return Json(new { IsCreated = false, ErrorMessage = 'My error message');


     type: "POST",
     dataType: "json",
     url: "MyController/Create",
     data: JSON.stringify(myObject),
     success: function (result) {
    //... ALL FINE
    //... Use input may be wrong but nothing crashed
    error: function (error) {
            alert("Error:" + erro.responseJSON.ErrorMessage ); //Error

Choice between vector::resize() and vector::reserve()

reserve when you do not want the objects to be initialized when reserved. also, you may prefer to logically differentiate and track its count versus its use count when you resize. so there is a behavioral difference in the interface - the vector will represent the same number of elements when reserved, and will be 100 elements larger when resized in your scenario.

Is there any better choice in this kind of scenario?

it depends entirely on your aims when fighting the default behavior. some people will favor customized allocators -- but we really need a better idea of what it is you are attempting to solve in your program to advise you well.

fwiw, many vector implementations will simply double the allocated element count when they must grow - are you trying to minimize peak allocation sizes or are you trying to reserve enough space for some lock free program or something else?

How To Format A Block of Code Within a Presentation?

An on-line syntax highlighter:


Just copy and paste into your document.

Add an element to an array in Swift

Example: students = ["Ben" , "Ivy" , "Jordell"]

1) To add single elements to the end of an array, use the append(_:)

students.append(\ "Maxime" )

2) Add multiple elements at the same time by passing another array or a sequence of any kind to the append(contentsOf:) method

students.append(contentsOf: ["Shakia" , "William"])

3) To add new elements in the middle of an array by using the insert(_:at:) method for single elements

students.insert("Liam" , at:2 )

4) Using insert(contentsOf:at:) to insert multiple elements from another collection or array literal

students.insert(['Tim','TIM' at: 2 )

How to enable CORS in ASP.NET Core

In case you get the error "No 'Access-Control-Allow-Origin' header is present on the requested resource." Specifically for PUT and DELETE requests, you could try to disable WebDAV on IIS.

Apparently, the WebDAVModule is enabled by default and is disabling PUT and DELETE requests by default.

To disable the WebDAVModule, add this to your web.config:

  <modules runAllManagedModulesForAllRequests="false">
    <remove name="WebDAVModule" />

What is a CSRF token? What is its importance and how does it work?

The site generates a unique token when it makes the form page. This token is required to post/get data back to the server.

Since the token is generated by your site and provided only when the page with the form is generated, some other site can't mimic your forms -- they won't have the token and therefore can't post to your site.

How to find the Vagrant IP?

Terminating a connection open with vagrant ssh will show the address, so a dummy or empty command can be executed:

$ vagrant ssh -c ''
Connection to closed.

JSON.parse vs. eval()

Not all browsers have native JSON support so there will be times where you need to use eval() to the JSON string. Use JSON parser from as that handles everything a lot easier for you.

Eval() is an evil but against some browsers its a necessary evil but where you can avoid it, do so!!!!!

Display more Text in fullcalendar

I needed the ability to display quite a bit of info (without a tooltip) and it turned out quite nice. I used FullCalendars title prop to store all my HTML. The only thing you have to do to ensure it works after render is to parse the title fields HTML.

// `data` ismy JSON object.
$.each(data, function(index, value) {
  value.title = '<div class="title">' + value.title + '</div>';
  value.title += '<div class="deets"><span class="time"><img src="/themes/custom/bp/images/clock.svg">' + value.start_time + ' - ' + value.end_time + '</span>';
  value.title += '<span class="location"><img src="/themes/custom/bp/images/pin.svg">' + value.location + '</span></div>';
  value.title += '<div class="learn-more">LEARN MORE <span class="arrow"></span></span>';

// Initialize the calendar object.
calendar = new FullCalendar.Calendar(cal, {
  events: data,
  plugins: ['dayGrid'],
  eventRender: function(event) {
    // This is required to parse the HTML.
    const title = $(event.el).find('.fc-title');

I would have used template literals, but had to support IE11


Can I append an array to 'formdata' in javascript?

use "xxx[]" as name of the field in formdata (you will get an array of - stringified objects - in you case)

so within your loop

            article = $(this).find('input[name="article"]').val();
            gender = $(this).find('input[name="gender"]').val();
            brand = $(this).find('input[name="brand"]').val();
            this_tag = new Array();
            this_tag.article = article;
            this_tag.gender = gender;
            this_tag.brand = brand;
            formdata.append('tags[]', this_tag);

How to get dictionary values as a generic list

Dictionary<string, MyType> myDico = GetDictionary();

var items = myDico.Select(d=> d.Value).ToList();

Parsing xml using powershell

[xml]$xmlfile = '<xml> <Section name="BackendStatus"> <BEName BE="crust" Status="1" /> <BEName BE="pizza" Status="1" /> <BEName BE="pie" Status="1" /> <BEName BE="bread" Status="1" /> <BEName BE="Kulcha" Status="1" /> <BEName BE="kulfi" Status="1" /> <BEName BE="cheese" Status="1" /> </Section> </xml>'

foreach ($bename in $xmlfile.xml.Section.BEName) {
    if($bename.Status -eq 1){
        #Do something

Adding elements to object

function addValueInObject(object, key, value) {
    var res = {};
    var textObject = JSON.stringify(object);
    if (textObject === '{}') {
        res = JSON.parse('{"' + key + '":"' + value + '"}');
    } else {
        res = JSON.parse('{' + textObject.substring(1, textObject.length - 1) + ',"' + key + '":"' + value + '"}');
    return res;

this code is worked.

Check if String / Record exists in DataTable

Use the Find method if item_manuf_id is a primary key:

var result = dtPs.Rows.Find("some value");

If you only want to know if the value is in there then use the Contains method.

if (dtPs.Rows.Contains("some value"))

Primary key restriction applies to Contains aswell.

How to use a Java8 lambda to sort a stream in reverse order?

You can use a method reference:

import static java.util.Comparator.*;
import static*;

    .filter(file -> isNameLikeBaseLine(file, baseLineFile.getName()))
    .forEach(item -> item.delete());

In alternative of method reference you can use a lambda expression, so the argument of comparing become:

.sorted(comparing(file -> file.lastModified()).reversed());

How do I add a reference to the MySQL connector for .NET?

This is an older question, but I found it yesterday while struggling with getting the MySQL Connector reference working properly on examples I'd found on the web. I'm working with VS 2010 on Win7 64 bit but have to work with .NET 3.5.

As others have stated, you need to download the .Net & Mono versions (I don't know why this is true, but it's what I've found works). The link to the connectors is given above in the earlier answers.

  • Extract the connectors somewhere convenient.
  • Open the project in Visual Studio, then on the menu bar navigate to Solution Explorer (View > Solution Explorer), and choose Properties (first box on the far left of the toolbar. The Solution Explorer shows up in the top right pane for me, but YMMV).
  • In Properties, select References & locate the instance for It's likely to have a yellow bang on it (Yellow triangle with exclamation point in it). Remove it.
  • Then on the menu bar, navigate to Project > Add Reference... > Browse > point to where you downloaded the connectors. I have only been able to get the V2 version to work, but that may be a factor of my platform, not sure.
  • Clean & build your application. You should now be able to use the MySQL connectors to talk to your database.
  • You can also now downgrade your .NET instance if you need to (we're constrained to .NET 3.5, but wants 4.0 at the time of my writing this). On the menu bar, navigate to the properties of your project (Project > Properties). Choose the Application tab > Target framework > Choose which .NET framework you want to use. You have to build the application at least once before you can change the .NET framework. Once you built once the connector will no longer complain about the lower version of .NET.

How do I call a JavaScript function on page load?

here's the trick (works everywhere):

alert('DOM Ready!');
function r(f){/in/.test(document.readyState)?setTimeout('r('+f+')',9):f()}

Python + Django page redirect

It's simple:

from django.http import HttpResponseRedirect

def myview(request):
    return HttpResponseRedirect("/path/")

More info in the official Django docs

Update: Django 1.0

There is apparently a better way of doing this in Django now using generic views.

Example -

from django.views.generic.simple import redirect_to

urlpatterns = patterns('',   
    (r'^one/$', redirect_to, {'url': '/another/'}),


There is more in the generic views documentation. Credit - Carles Barrobés.

Update #2: Django 1.3+

In Django 1.5 redirect_to no longer exists and has been replaced by RedirectView. Credit to Yonatan

from django.views.generic import RedirectView

urlpatterns = patterns('',
    (r'^one/$', RedirectView.as_view(url='/another/')),

How to convert std::string to LPCWSTR in C++ (Unicode)

string  myMessage="helloworld";
int len;
int slength = (int)myMessage.length() + 1;
len = MultiByteToWideChar(CP_ACP, 0, myMessage.c_str(), slength, 0, 0); 
wchar_t* buf = new wchar_t[len];
MultiByteToWideChar(CP_ACP, 0, myMessage.c_str(), slength, buf, len);
std::wstring r(buf);
 std::wstring stemp = r.C_str();
LPCWSTR result = stemp.c_str();

How to concat a string to xsl:value-of select="...?

The easiest way to concat a static text string to a selected value is to use element.

  <xsl:attribute name="href"> 
    <xsl:value-of select="/*/properties/property[@name='report']/@value" />

how to add the missing RANDR extension

First off, Xvfb doesn't read configuration from xorg.conf. Xvfb is a variant of the KDrive X servers and like all members of that family gets its configuration from the command line.

It is true that XRandR and Xinerama are mutually exclusive, but in the case of Xvfb there's no Xinerama in the first place. You can enable the XRandR extension by starting Xvfb using at least the following command line options

Xvfb +extension RANDR [further options]

Convert bytes to bits in python

Operations are much faster when you work at the integer level. In particular, converting to a string as suggested here is really slow.

If you want bit 7 and 8 only, use e.g.

val = (byte >> 6) & 3

(this is: shift the byte 6 bits to the right - dropping them. Then keep only the last two bits 3 is the number with the first two bits set...)

These can easily be translated into simple CPU operations that are super fast.

Passing an array using an HTML form hidden element

If you want to post an array you must use another notation:

foreach ($postvalue as $value){
<input type="hidden" name="result[]" value="$value.">

in this way you have three input fields with the name result[] and when posted $_POST['result'] will be an array

Find a pair of elements from an array whose sum equals a given number

C++11, run time complexity O(n):

#include <vector>
#include <unordered_map>
#include <utility>

std::vector<std::pair<int, int>> FindPairsForSum(
        const std::vector<int>& data, const int& sum)
    std::unordered_map<int, size_t> umap;
    std::vector<std::pair<int, int>> result;
    for (size_t i = 0; i < data.size(); ++i)
        if (0 < umap.count(sum - data[i]))
            size_t j = umap[sum - data[i]];
            result.push_back({data[i], data[j]});
            umap[data[i]] = i;

    return result;

Second line in li starts under the bullet after CSS-reset

I second Dipaks' answer, but often just the text-indent is enough as you may/maynot be positioning the ul for better layout control.

ul li{
text-indent: -1em;

Why doesn't JavaScript support multithreading?

Just as matt b said, the question is not very clear. Assuming that you are asking about multithreading support in the language: because it isn't needed for 99.999% of the applications running in the browser currently. If you really need it, there are workarounds (like using window.setTimeout).

In general multithreading is very, very, very, very, very, very hard (did I say that it is hard?) to get right, unless you put in extra restrictions (like using only immutable data).

Why does 2 mod 4 = 2?

This could be a good time to mention the modr() function. It returns both the whole and the remainder parts of a division.

print("\n 17 // 3 =",17//3," # Does the same thing as int(17/3)")
print(" 17 %  3 =",17%3," # Modulo division gives the remainder.")
whole, remain = divmod(17,3)
print(" divmod(17,3) returns ->",divmod(17,3),end="")
print(" because 3 goes into 17,",whole,"times with a remainder of",remain,end=".\n\n")

Floating elements within a div, floats outside of div. Why?

Here's more modern approach:

.parent {display: flow-root;} 

No more clearfixes.

p.s. Using overflow: hidden; hides the box-shadow so...

jQuery: find element by text

Best way in my opinion.

$.fn.findByContentText = function (text) {
    return $(this).contents().filter(function () {
        return $(this).text().trim() == text.trim();

Why use the params keyword?

Might sound stupid, But Params doesn't allow multidimensional array. Whereas you can pass a multidimensional array to a function.

How eliminate the tab space in the column in SQL Server 2008

Try this code

SELECT REPLACE([Column], char(9), '') From [dbo.Table] 

char(9) is the TAB character

PowerShell try/catch/finally

That is very odd.

I went through ItemNotFoundException's base classes and tested the following multiple catches to see what would catch it:

try {
  remove-item C:\nonexistent\file.txt -erroraction stop
catch [System.Management.Automation.ItemNotFoundException] {
  write-host 'ItemNotFound'
catch [System.Management.Automation.SessionStateException] {
  write-host 'SessionState'
catch [System.Management.Automation.RuntimeException] {
  write-host 'RuntimeException'
catch [System.SystemException] {
  write-host 'SystemException'
catch [System.Exception] {
  write-host 'Exception'
catch {
  write-host 'well, darn'

As it turns out, the output was 'RuntimeException'. I also tried it with a different exception CommandNotFoundException:

try {
catch [System.Management.Automation.CommandNotFoundException] {
  write-host 'CommandNotFoundException'
catch {
  write-host 'well, darn'

That output 'CommandNotFoundException' correctly.

I vaguely remember reading elsewhere (though I couldn't find it again) of problems with this. In such cases where exception filtering didn't work correctly, they would catch the closest Type they could and then use a switch. The following just catches Exception instead of RuntimeException, but is the switch equivalent of my first example that checks all base types of ItemNotFoundException:

try {
  Remove-Item C:\nonexistent\file.txt -ErrorAction Stop
catch [System.Exception] {
  switch($_.Exception.GetType().FullName) {
    'System.Management.Automation.ItemNotFoundException' {
      write-host 'ItemNotFound'
    'System.Management.Automation.SessionStateException' {
      write-host 'SessionState'
    'System.Management.Automation.RuntimeException' {
      write-host 'RuntimeException'
    'System.SystemException' {
      write-host 'SystemException'
    'System.Exception' {
      write-host 'Exception'
    default {'well, darn'}

This writes 'ItemNotFound', as it should.

How can I save an image with PIL?

Try removing the . before the .bmp (it isn't matching BMP as expected). As you can see from the error, the save_handler is upper-casing the format you provided and then looking for a match in SAVE. However the corresponding key in that object is BMP (instead of .BMP).

I don't know a great deal about PIL, but from some quick searching around it seems that it is a problem with the mode of the image. Changing the definition of j to:

j = Image.fromarray(b, mode='RGB')

Seemed to work for me (however note that I have very little knowledge of PIL, so I would suggest using @mmgp's solution as s/he clearly knows what they are doing :) ). For the types of mode, I used this page - hopefully one of the choices there will work for you.

ActiveXObject in Firefox or Chrome (not IE!)

No for the moment.

I doubt it will be possible for the future for ActiveX support will be discontinued in near future (as MS stated).

Look here about HTML Object tag, but not anything will be accepted. You should try.

Examples of Algorithms which has O(1), O(n log n) and O(log n) complexities

0(logn)-Binary search, peak element in an array(there can be more than one peak) 0(1)-in python calculating the length of a list or a string. The len() function takes 0(1) time. Accessing an element in an array takes 0(1) time. Push operation in a stack takes 0(1) time. 0(nlogn)-Merge sort. sorting in python takes nlogn time. so when you use listname.sort() it takes nlogn time.

Note-Searching in a hash table sometimes takes more than constant time because of collisions.

What is code coverage and how do YOU measure it?

In the previous answers Code coverage has been explained well . I am just adding some knowledge related to tools if your are working on iOS and OSX platforms, Xcode provides the facility to test and monitor code coverage.

Reference Links:

Both are helpful links for learning and exploring code coverage with Xcode.

Currency Formatting in JavaScript

You could use toPrecision() and toFixed() methods of Number type. Check this link How can I format numbers as money in JavaScript?

Two inline-block, width 50% elements wrap to second line

You can remove the whitespaces via css using white-space so you can keep your pretty HTML layout. Don't forget to set the white-space back to normal again if you want your text to wrap inside the columns.

Tested in IE9, Chrome 18, FF 12

.container { white-space: nowrap; }
.column { display: inline-block; width: 50%; white-space: normal; }

<div class="container">
  <div class="column">text that can wrap</div>
  <div class="column">text that can wrap</div>

File changed listener in Java

You may also consider the Apache Commons JCI (Java Compiler Interface). Although this API seems to be focused on dynamic compilation of classes, it also includes classes in its API that monitors file changes.


Strip spaces/tabs/newlines - python

Use the re library

import re
myString = "I want to Remove all white \t spaces, new lines \n and tabs \t"
myString = re.sub(r"[\n\t\s]*", "", myString)
print myString



How to iterate over a column vector in Matlab?

In Matlab, you can iterate over the elements in the list directly. This can be useful if you don't need to know which element you're currently working on.

Thus you can write

for elm = list
%# do something with the element

Note that Matlab iterates through the columns of list, so if list is a nx1 vector, you may want to transpose it.

Unable to copy file - access to the path is denied

I solved this problem by deleting the contentious files from bin folder and rebuilding the project.

Print a div using javascript in angularJS single page application

$scope.printDiv = function(divName) {
  var printContents = document.getElementById(divName).innerHTML;
  var popupWin ='', '_blank', 'width=300,height=300');;
  popupWin.document.write('<html><head><link rel="stylesheet" type="text/css" href="style.css" /></head><body onload="window.print()">' + printContents + '</body></html>');

UTF-8: General? Bin? Unicode?

In general, utf8_general_ci is faster than utf8_unicode_ci, but less correct.

Here is the difference:

For any Unicode character set, operations performed using the _general_ci collation are faster than those for the _unicode_ci collation. For example, comparisons for the utf8_general_ci collation are faster, but slightly less correct, than comparisons for utf8_unicode_ci. The reason for this is that utf8_unicode_ci supports mappings such as expansions; that is, when one character compares as equal to combinations of other characters. For example, in German and some other languages “ß” is equal to “ss”. utf8_unicode_ci also supports contractions and ignorable characters. utf8_general_ci is a legacy collation that does not support expansions, contractions, or ignorable characters. It can make only one-to-one comparisons between characters.

Quoted from:

For more detailed explanation, please read the following post from MySQL forums:,187048,188748

As for utf8_bin: Both utf8_general_ci and utf8_unicode_ci perform case-insensitive comparison. In constrast, utf8_bin is case-sensitive (among other differences), because it compares the binary values of the characters.

How can I debug a HTTP POST in Chrome?

  1. Go to Chrome Developer Tools (Chrome Menu -> More Tools -> Developer Tools)
  2. Choose "Network" tab
  3. Refresh the page you're on
  4. You'll get list of http queries that happened, while the network console was on. Select one of them in the left
  5. Choose "Headers" tab


enter image description here

How to redirect in a servlet filter?

If you also want to keep hash and get parameter, you can do something like this (fill redirectMap at filter init):

String uri = request.getRequestURI();

String[] uriParts = uri.split("[#?]");
String path = uriParts[0];
String rest = uri.substring(uriParts[0].length());

if(redirectMap.containsKey(path)) {
    response.sendRedirect(redirectMap.get(path) + rest);
} else {
    chain.doFilter(request, response);

Why is Tkinter Entry's get function returning nothing?

You could also use a StringVar variable, even if it's not strictly necessary:

v = StringVar()

e = Entry(master, textvariable=v)

v.set("a default value")
s = v.get()

For more information, see this page on

How do you set a JavaScript onclick event to a class with css

You could do it with jQuery.

$('.myClass').click(function() {

define() vs. const

I know this is already answered, but none of the current answers make any mention of namespacing and how it affects constants and defines.

As of PHP 5.3, consts and defines are similar in most respects. There are still, however, some important differences:

  • Consts cannot be defined from an expression. const FOO = 4 * 3; doesn't work, but define('CONST', 4 * 3); does.
  • The name passed to define must include the namespace to be defined within that namespace.

The code below should illustrate the differences.

namespace foo 
    const BAR = 1;
    define('BAZ', 2);
    define(__NAMESPACE__ . '\\BAZ', 3);

namespace {

The content of the user sub-array will be ['foo\\BAR' => 1, 'BAZ' => 2, 'foo\\BAZ' => 3].

=== UPDATE ===

The upcoming PHP 5.6 will allow a bit more flexibility with const. You will now be able to define consts in terms of expressions, provided that those expressions are made up of other consts or of literals. This means the following should be valid as of 5.6:

const FOOBAR = 'foo ' . 'bar';
const FORTY_TWO = 6 * 9; // For future editors: THIS IS DELIBERATE! Read the answer comments below for more details
const ULTIMATE_ANSWER = 'The ultimate answer to life, the universe and everything is ' . FORTY_TWO;

You still won't be able to define consts in terms of variables or function returns though, so

const RND = mt_rand();
const CONSTVAR = $var;

will still be out.

Shell script to check if file exists

for entry in "/home/loc/etc/"/*

   if [ -s /home/loc/etc/$entry ]
       echo "$entry File is available"
       echo "$entry File is not available"

Hope it helps

How to concatenate strings with padding in sqlite

The || operator is "concatenate" - it joins together the two strings of its operands.


For padding, the seemingly-cheater way I've used is to start with your target string, say '0000', concatenate '0000423', then substr(result, -4, 4) for '0423'.

Update: Looks like there is no native implementation of "lpad" or "rpad" in SQLite, but you can follow along (basically what I proposed) here:

-- the statement below is almost the same as
-- select lpad(mycolumn,'0',10) from mytable

select substr('0000000000' || mycolumn, -10, 10) from mytable

-- the statement below is almost the same as
-- select rpad(mycolumn,'0',10) from mytable

select substr(mycolumn || '0000000000', 1, 10) from mytable

Here's how it looks:

SELECT col1 || '-' || substr('00'||col2, -2, 2) || '-' || substr('0000'||col3, -4, 4)

it yields


Converting HTML to PDF using PHP?

If you wish to create a pdf from php, pdflib will help you (as some others suggested).

Else, if you want to convert an HTML page to PDF via PHP, you'll find a little trouble outta here.. For 3 years I've been trying to do it as best as I can.

So, the options I know are:

DOMPDF : php class that wraps the html and builds the pdf. Works good, customizable (if you know php), based on pdflib, if I remember right it takes even some CSS. Bad news: slow when the html is big or complex.

HTML2PS: same as DOMPDF, but this one converts first to a .ps (ghostscript) file, then, to whatever format you need (pdf, jpg, png). For me is little better than dompdf, but has the same speed problem.. but, better compatibility with CSS.

Those two are php classes, but if you can install some software on the server, and access it throught passthru() or system(), give a look to these too:

wkhtmltopdf: based on webkit (safari's wrapper), is really fast and powerful.. seems like this is the best one (atm) for converting html pages to pdf on the fly; taking only 2 seconds for a 3 page xHTML document with CSS2. It is a recent project, anyway, the google.code page is often updated.

htmldoc : This one is a tank, it never really stops/crashes.. the project looks dead since 2007, but anyway if you don't need CSS compatibility this can be nice for you.

'dependencies.dependency.version' is missing error, but version is managed in parent

If anyone finds their way here with the same problem I was having, my problem was that I was missing the <dependencyManagement> tags around dependencies I had copied from the child pom.

How to fix Uncaught InvalidValueError: setPosition: not a LatLng or LatLngLiteral: in property lat: not a number?

I was having the same problem, the fact is that the input of lat and long should be String. Only then did I manage.

for example:


 ViewBag.Lat = object.Lat.ToString().Replace(",", ".");

 ViewBag.Lng = object.Lng.ToString().Replace(",", ".");

View - function javascript

    function initMap() {
        var myLatLng = { lat: @ViewBag.Lat, lng: @ViewBag.Lng};

        // Create a map object and specify the DOM element for display.
        var map = new'map'),
            center: myLatLng,
            scrollwheel: false,
            zoom: 16

        // Create a marker and set its position.
        var marker = new{
            map: map,
            position: myLatLng
            //title: "Blue"

I convert the double value to string and do a Replace in the ',' to '.' And so everything works normally.

Extract first item of each sublist

Had the same issue and got curious about the performance of each solution.

Here's is the %timeit:

import numpy as np
lst = [['a','b','c'], [1,2,3], ['x','y','z']]

The first numpy-way, transforming the array:

%timeit list(np.array(lst).T[0])
4.9 µs ± 163 ns per loop (mean ± std. dev. of 7 runs, 100000 loops each)

Fully native using list comprehension (as explained by @alecxe):

%timeit [item[0] for item in lst]
379 ns ± 23.1 ns per loop (mean ± std. dev. of 7 runs, 1000000 loops each)

Another native way using zip (as explained by @dawg):

%timeit list(zip(*lst))[0]
585 ns ± 7.26 ns per loop (mean ± std. dev. of 7 runs, 1000000 loops each)

Second numpy-way. Also explained by @dawg:

%timeit list(np.array(lst)[:,0])
4.95 µs ± 179 ns per loop (mean ± std. dev. of 7 runs, 100000 loops each)

Surprisingly (well, at least for me) the native way using list comprehension is the fastest and about 10x faster than the numpy-way. Running the two numpy-ways without the final list saves about one µs which is still in the 10x difference.

Note that, when I surrounded each code snippet with a call to len, to ensure that Generators run till the end, the timing stayed the same.

How to get previous page url using jquery

simple & sweet

window.location = document.referrer;

Boto3 Error: botocore.exceptions.NoCredentialsError: Unable to locate credentials

If you're sure you configure your aws correctly, just make sure the user of the project can read from ./aws or just run your project as a root

Sourcetree - undo unpushed commits

If you select the log entry to which you want to revert to then you can click on "Reset to this commit". Only use this option if you didn't push the reverse commit changes. If you're worried about losing the changes then you can use the soft mode which will leave a set of uncommitted changes (what you just changed). Using the mixed resets the working copy but keeps those changes, and a hard will just get rid of the changes entirely. Here's some screenshots:

enter image description here

How do I revert back to an OpenWrt router configuration?

Those who are facing this problem: Don't panic.

Short answer:

Restart your router, and this problem will be fixed. (But if your restart button is not working, you need to do a nine-step process to do the restart. Hitting the restart button is just one of them.)

Long answer: Let's learn how to restart the router.

  1. Set your PC's IP address: and subnetmask and gateway
  2. Power off the router
  3. Disconnect the WAN cable
  4. Only connect your PC Ethernet cable to ETH0
  5. Power on the router
  6. Wait for the router to start the boot sequence (SYS LED starts blinking)
  7. When the SYS LED is blinking, hit the restart button (the SYS LED will be blinking at a faster rate means your router is in failsafe mode). (You have to hit the button before the router boots.)
  8. telnet
  9. Run these commands:

    mount_root ## this remounts your partitions from read-only to read/write mode
    firstboot  ## This will reset your router after reboot
    reboot -f ## And force reboot
  10. Log in the web interface using web browser.

link to see the official failsafe mode.

How do I add a delay in a JavaScript loop?

Here is a function that I use for looping over an array:

function loopOnArrayWithDelay(theArray, delayAmount, i, theFunction, onComplete){

    if (i < theArray.length && typeof delayAmount == 'number'){

        console.log("i "+i);

        theFunction(theArray[i], i);


            loopOnArrayWithDelay(theArray, delayAmount, (i+1), theFunction, onComplete)}, delayAmount);


You use it like this:

loopOnArrayWithDelay(YourArray, 1000, 0, function(e, i){
    //Do something with item
}, function(i){
    //Do something once loop has completed

Form inside a form, is that alright?

Form nesting can be achieved with new HTML5 input element's form attribute. Although we don't nest forms structurally, inputs are evaluated as they are in their own form. In my tests, 3 major browsers support this except IE(IE11). Form nesting limitation was a big obstacle for HTML UI design.

Here is a sample code, when you click Save button you should see "2 3 success" (Original

<form id="saveForm" action="/post/dispatch/save" method="post"></form>
<form id="deleteForm" action="/post/dispatch/delete" method="post"></form>

<div id="toolbar">
    <input type="text" name="foo" form="saveForm" />
    <input type="hidden" value="some_id" form="deleteForm" />
    <input type="text" name="foo2" id="foo2" form="saveForm" value="success" />

    <input type="submit" name="save" value="Save" form="saveForm" onclick="alert(document.getElementById('deleteForm').elements.length + ' ' + document.getElementById('saveForm').elements.length + ' ' + document.getElementById('saveForm').elements['foo2'].value);return false;" />
    <input type="submit" name="delete" value="Delete" form="deleteForm" />
    <a href="/home/index">Cancel</a>

Disable cache for some images

Browser caching strategies can be controlled by HTTP headers. Remember that they are just a hint, really. Since browsers are terribly inconsistent in this (and any other) field, you'll need several headers to get the desired effect on a range of browsers.

header ("Pragma-directive: no-cache");
header ("Cache-directive: no-cache");
header ("Cache-control: no-cache");
header ("Pragma: no-cache");
header ("Expires: 0");

Use string in switch case in java

Just to make concrete emory's answer, the executable code is the following :

  Map<String,Callable<USer>> map = new HashMap<String,Callable<User>>();
  map.put( "test" , new Callable<User> () { public User call (){ return fillUser("test" ); }} ) ;
  map.put( "admin" , new Callable<Utente> () { public Utente call (){  return fillUser("admin" ); }} ) ;

where user is a POJO, and then

  User user = map.get(USERNAME).call();

finally the called method is somewhere :

 private User fillUser(String x){        
        User user = new User();
        // set something in User
        return user;

How to read an external properties file in Maven

Using the suggested Maven properties plugin I was able to read in a file that I use to version my builds.


Is there a way to pass optional parameters to a function?

You can specify a default value for the optional argument with something that would never passed to the function and check it with the is operator:

class _NO_DEFAULT:
    def __repr__(self):return "<no default>"

def func(optional= _NO_DEFAULT):
    if optional is _NO_DEFAULT:
        print("the optional argument was not passed")
        print("the optional argument was:",optional)

then as long as you do not do func(_NO_DEFAULT) you can be accurately detect whether the argument was passed or not, and unlike the accepted answer you don't have to worry about side effects of ** notation:

# these two work the same as using **

# the optional argument can be positional or keyword unlike using **

#this correctly raises an error where as it would need to be explicitly checked when using **

How to find the size of an int[]?

You can make a template function, and pass the array by reference to achieve this.

Here is my code snippet

template <typename TypeOfData>

void PrintArray(TypeOfData &arrayOfType);

int main()


    char charArray[] = "my name is";

    int intArray[] = { 1,2,3,4,5,6 };

    double doubleArray[] = { 1.1,2.2,3.3 };





template <typename TypeOfData>

void PrintArray(TypeOfData &arrayOfType)


    int elementsCount = sizeof(arrayOfType) / sizeof(arrayOfType[0]);

    for (int i = 0; i < elementsCount; i++)


        cout << "Value in elements at position " << i + 1 << " is " << arrayOfType[i] << endl;



What is the difference between a pandas Series and a single-column DataFrame?

Import cars data

import pandas as pd

cars = pd.read_csv('cars.csv', index_col = 0)

Here is how the cars.csv file looks.

Print out drives_right column as Series:


    US      True
    AUS    False
    JAP    False
    IN     False
    RU      True
    MOR     True
    EG      True
    Name: drives_right, dtype: bool

The single bracket version gives a Pandas Series, the double bracket version gives a Pandas DataFrame.

Print out drives_right column as DataFrame


    US           True
    AUS         False
    JAP         False
    IN          False
    RU           True
    MOR          True
    EG           True

Adding a Series to another Series creates a DataFrame.

Markdown to create pages and table of contents?

MultiMarkdown Composer does seem to generate a table of contents to assist while editing.

There might also be the one or the other library, who can generate TOCs: see Python Markdown TOC Extension.

The HTTP request is unauthorized with client authentication scheme 'Ntlm'

I had to move domain, username, password from

client.ClientCredentials.UserName.UserName = domain + "\\" + username; client.ClientCredentials.UserName.Password = password


client.ClientCredentials.Windows.ClientCredential.UserName = username; client.ClientCredentials.Windows.ClientCredential.Password = password; client.ClientCredentials.Windows.ClientCredential.Domain = domain;

How to select last child element in jQuery?

By using the :last-child selector?

Do you have a specific scenario in mind you need assistance with?

Where does MAMP keep its php.ini?

Change /Applications/MAMP/conf/php5.2/php.ini if you are using 5.2 version of php. If you are using the 5.3 php version, edit the /Applications/MAMP/conf/php5.3/php.ini.

If you are using OSX Lion or OSX Mountain Lion, I recommend you using the default installation of apache and php.


Bootstrap 3 Align Text To Bottom of Div

I think your best bet would be to use a combination of absolute and relative positioning.

Here's a fiddle:

given your html:

<div class="row">
    <div class="col-sm-6">
        <img src="~/Images/MyLogo.png" alt="Logo" />
    <div class="bottom-align-text col-sm-6">
        <h3>Some Text</h3>

use the following CSS:

@media (min-width: 768px ) {
  .row {
      position: relative;

  .bottom-align-text {
    position: absolute;
    bottom: 0;
    right: 0;

EDIT - Fixed CSS and JSFiddle for mobile responsiveness and changed the ID to a class.

Make selected block of text uppercase

I'm using the change-case extension and it works fine. I defined the shortcuts:

  "key": "ctrl+shift+u", 
  "command": "extension.changeCase.upper", 
  "when": "editorTextFocus" 
  "key": "ctrl+u",
  "command": "extension.changeCase.lower", 
  "when": "editorTextFocus" 

Excel formula to remove space between words in a cell

Steps (1) Just Select your range, rows or column or array , (2) Press ctrl+H , (3 a) then in the find type a space (3 b) in the replace do not enter anything, (4)then just click on replace all..... you are done.

OOP vs Functional Programming vs Procedural

I think the available libraries, tools, examples, and communities completely trumps the paradigm these days. For example, ML (or whatever) might be the ultimate all-purpose programming language but if you can't get any good libraries for what you are doing you're screwed.

For example, if you're making a video game, there are more good code examples and SDKs in C++, so you're probably better off with that. For a small web application, there are some great Python, PHP, and Ruby frameworks that'll get you off and running very quickly. Java is a great choice for larger projects because of the compile-time checking and enterprise libraries and platforms.

It used to be the case that the standard libraries for different languages were pretty small and easily replicated - C, C++, Assembler, ML, LISP, etc.. came with the basics, but tended to chicken out when it came to standardizing on things like network communications, encryption, graphics, data file formats (including XML), even basic data structures like balanced trees and hashtables were left out!

Modern languages like Python, PHP, Ruby, and Java now come with a far more decent standard library and have many good third party libraries you can easily use, thanks in great part to their adoption of namespaces to keep libraries from colliding with one another, and garbage collection to standardize the memory management schemes of the libraries.

How to activate an Anaconda environment

All the former answers seem to be outdated.

conda activate was introduced in conda 4.4 and 4.6.

conda activate: The logic and mechanisms underlying environment activation have been reworked. With conda 4.4, conda activate and conda deactivate are now the preferred commands for activating and deactivating environments. You’ll find they are much more snappy than the source activate and source deactivate commands from previous conda versions. The conda activate command also has advantages of (1) being universal across all OSes, shells, and platforms, and (2) not having path collisions with scripts from other packages like python virtualenv’s activate script.


conda create -n venv-name python=3.6
conda activate -n venv-name
conda deactivate

These new sub-commands are available in "Aanconda Prompt" and "Anaconda Powershell Prompt" automatically. To use conda activate in every shell (normal cmd.exe and powershell), check expose conda command in every shell on Windows.


Edit and Continue: "Changes are not allowed when..."

For me, it was happening after I had hit a breakpoint, had done some edits, then continued on stepping through the code, then finally hit F5 or "Continue" to get to the end and out of my code block.

After trying the "delete all breakpoints" option (Ctrl+Shift+PrtScn and OK on the prompt) and doing a Rebuild All, I still had an error in my Error Log with regard to my DLL for my project not loading... "Can't apply changes, x.DLL not loaded". After restarting Visual Studio, all was fine again. For me, it turned out to be just this simple.

Other things here did not work for me, like "Require source files to exactly match the original version" was checked before and after things started working again just fine, and targeting "Any CPU" on my x64 machine is just fine, too (did not need to specify x86 or x64). I had "Enable Edit and Continue" enabled in my Tools > Options > Debugging and in my Project Properties > "Web" tab settings.

stop service in android

To stop the service we must use the method stopService():

  Intent myService = new Intent(MainActivity.this, BackgroundSoundService.class);

then the method onDestroy() in the service is called:

    public void onDestroy() {

        Log.i(TAG, "onCreate() , service stopped...");

Here is a complete example including how to stop the service.

How do I make a request using HTTP basic authentication with PHP curl?

The most simple and native way it's to use CURL directly.

This works for me :

$login = 'login';
$password = 'password';
$url = 'http://your.url';
$ch = curl_init();
curl_setopt($ch, CURLOPT_URL,$url);
curl_setopt($ch, CURLOPT_RETURNTRANSFER,1);
curl_setopt($ch, CURLOPT_USERPWD, "$login:$password");
$result = curl_exec($ch);