Difference between AutoPostBack=True and AutoPostBack=False?
The AutoPostBack property is used to set or return whether or not an automatic post back occurs when the user presses "ENTER" or "TAB" in the TextBox control.
If this property is set to TRUE the automatic post back is enabled, otherwise FALSE. Default is FALSE.
Why did a network-related or instance-specific error occur while establishing a connection to SQL Server?
If your server was working and suddenly started erroring out, your server/instance stopped and connection settings were changed somehow.
For SQL Server 2008 here is how you can fit this:
- Goto
Start > All Programs > SQL Server 2008 > Configuration Tools > SQL Server Configuration Manager > SQL Server Services
.
And here you'll see all the instances and their state.
- The state of the instance you were trying to connect can be stopped here.
- Double click on the instance and then click on connect.
- It will connect and now go back and run your application, you will be able to connect with no error.
This solution assumes the error is not being caused by something wrong in your connection string.
Popup window in winform c#
Forms in C# are classes that inherit the Form
base class.
You can show a popup by creating an instance of the class and calling ShowDialog()
.
Basic Apache commands for a local Windows machine
For frequent uses of this command I found it easy to add the location of C:\xampp\apache\bin
to the PATH
. Use whatever directory you have this installed in.
Then you can run from any directory in command line:
httpd -k restart
The answer above that suggests httpd -k -restart is actually a typo. You can see the commands by running httpd /?
Critical t values in R
Extending @Ryogi answer above, you can take advantage of the lower.tail
parameter like so:
qt(0.25/2, 40, lower.tail = FALSE)
# 75% confidence
qt(0.01/2, 40, lower.tail = FALSE)
# 99% confidence
Import Excel Data into PostgreSQL 9.3
You can handle loading the excel file content by writing Java code using Apache POI library (https://poi.apache.org/). The library is developed for working with MS office application data including Excel.
I have recently created the application based on the technology that will help you to load Excel files to the Postgres database. The application is available under http://www.abespalov.com/. The application is tested only for Windows, but should work for Linux as well.
The application automatically creates necessary tables with the same columns as in the Excel files and populate the tables with content. You can export several files in parallel. You can skip the step to convert the files into the CSV format. The application handles the xls and xlsx formats.
Overall application stages are :
- Load the excel file content. Here is the code depending on file extension:
{
fileExtension = FilenameUtils.getExtension(inputSheetFile.getName());
if (fileExtension.equalsIgnoreCase("xlsx")) {
workbook = createWorkbook(openOPCPackage(inputSheetFile));
} else {
workbook =
createWorkbook(openNPOIFSFileSystemPackage(inputSheetFile));
}
sheet = workbook.getSheetAt(0);
}
- Establish Postgres JDBC connection
- Create a Postgres table
- Iterate over the sheet and inset rows into the table. Here is a piece of Java code :
{
Iterator<Row> rowIterator = InitInputFilesImpl.sheet.rowIterator();
//skip a header
if (rowIterator.hasNext()) {
rowIterator.next();
}
while (rowIterator.hasNext()) {
Row row = (Row) rowIterator.next();
// inserting rows
}
}
Here you can find all Java code for the application created for exporting excel to Postgres (https://github.com/palych-piter/Excel2DB).
How to list all Git tags?
Listing the available tags in Git is straightforward. Just type git tag
(with optional -l
or --list
).
$ git tag
v5.5
v6.5
You can also search for tags that match a particular pattern.
$ git tag -l "v1.8.5*"
v1.8.5
v1.8.5-rc0
v1.8.5-rc1
v1.8.5-rc2
Getting latest tag on git repository
The command finds the most recent tag that is reachable from a commit. If the tag points to the commit, then only the tag is shown. Otherwise, it suffixes the tag name with the number of additional commits on top of the tagged object and the abbreviated object name of the most recent commit.
git describe
With --abbrev
set to 0
, the command can be used to find the closest tagname
without any suffix:
git describe --abbrev=0
Other examples:
git describe --abbrev=0 --tags # gets tag from current branch
git describe --tags `git rev-list --tags --max-count=1` // gets tags across all branches, not just the current branch
How to prune local git tags that don't exist on remote
To put it simple, if you are trying to do something like git fetch -p -t
, it will not work starting with git version 1.9.4
.
However, there is a simple workaround that still works in latest versions:
git tag -l | xargs git tag -d // remove all local tags
git fetch -t // fetch remote tags
Globally catch exceptions in a WPF application?
In addition what others mentioned here, note that combining the Application.DispatcherUnhandledException
(and its similars) with
<configuration>
<runtime>
<legacyUnhandledExceptionPolicy enabled="1" />
</runtime>
</configuration>
in the app.config
will prevent your secondary threads exception from shutting down the application.
Spring Boot JPA - configuring auto reconnect
Setting spring.datasource.tomcat.testOnBorrow=true
in application.properties didn't work.
Programmatically setting like below worked without any issues.
import org.apache.tomcat.jdbc.pool.DataSource;
import org.apache.tomcat.jdbc.pool.PoolProperties;
@Bean
public DataSource dataSource() {
PoolProperties poolProperties = new PoolProperties();
poolProperties.setUrl(this.properties.getDatabase().getUrl());
poolProperties.setUsername(this.properties.getDatabase().getUsername());
poolProperties.setPassword(this.properties.getDatabase().getPassword());
//here it is
poolProperties.setTestOnBorrow(true);
poolProperties.setValidationQuery("SELECT 1");
return new DataSource(poolProperties);
}
How to force 'cp' to overwrite directory instead of creating another one inside?
You can do this using -T
option in cp
.
See Man page for cp
.
-T, --no-target-directory
treat DEST as a normal file
So as per your example, following is the file structure.
$ tree test
test
|-- bar
| |-- a
| `-- b
`-- foo
|-- a
`-- b
2 directories, 4 files
You can see the clear difference when you use -v
for Verbose.
When you use just -R
option.
$ cp -Rv foo/ bar/
`foo/' -> `bar/foo'
`foo/b' -> `bar/foo/b'
`foo/a' -> `bar/foo/a'
$ tree
|-- bar
| |-- a
| |-- b
| `-- foo
| |-- a
| `-- b
`-- foo
|-- a
`-- b
3 directories, 6 files
When you use the option -T
it overwrites the contents, treating the destination like a normal file and not directory.
$ cp -TRv foo/ bar/
`foo/b' -> `bar/b'
`foo/a' -> `bar/a'
$ tree
|-- bar
| |-- a
| `-- b
`-- foo
|-- a
`-- b
2 directories, 4 files
This should solve your problem.
How to get the number of characters in a string
You can try RuneCountInString
from the utf8 package.
returns the number of runes in p
that, as illustrated in this script: the length of "World" might be 6 (when written in Chinese: "??"), but its rune count is 2:
package main
import "fmt"
import "unicode/utf8"
func main() {
fmt.Println("Hello, ??", len("??"), utf8.RuneCountInString("??"))
}
Phrozen adds in the comments:
Actually you can do len()
over runes by just type casting.
len([]rune("??"))
will print 2
. At leats in Go 1.3.
And with CL 108985 (May 2018, for Go 1.11), len([]rune(string))
is now optimized. (Fixes issue 24923)
The compiler detects len([]rune(string))
pattern automatically, and replaces it with for r := range s call.
Adds a new runtime function to count runes in a string.
Modifies the compiler to detect the pattern len([]rune(string))
and replaces it with the new rune counting runtime function.
RuneCount/lenruneslice/ASCII 27.8ns ± 2% 14.5ns ± 3% -47.70%
RuneCount/lenruneslice/Japanese 126ns ± 2% 60 ns ± 2% -52.03%
RuneCount/lenruneslice/MixedLength 104ns ± 2% 50 ns ± 1% -51.71%
Stefan Steiger points to the blog post "Text normalization in Go"
What is a character?
As was mentioned in the strings blog post, characters can span multiple runes.
For example, an 'e
' and '?´?´' (acute "\u0301") can combine to form 'é' ("e\u0301
" in NFD). Together these two runes are one character.
The definition of a character may vary depending on the application.
For normalization we will define it as:
- a sequence of runes that starts with a starter,
- a rune that does not modify or combine backwards with any other rune,
- followed by possibly empty sequence of non-starters, that is, runes that do (typically accents).
The normalization algorithm processes one character at at time.
Using that package and its Iter
type, the actual number of "character" would be:
package main
import "fmt"
import "golang.org/x/text/unicode/norm"
func main() {
var ia norm.Iter
ia.InitString(norm.NFKD, "école")
nc := 0
for !ia.Done() {
nc = nc + 1
ia.Next()
}
fmt.Printf("Number of chars: %d\n", nc)
}
Here, this uses the Unicode Normalization form NFKD "Compatibility Decomposition"
Oliver's answer points to UNICODE TEXT SEGMENTATION as the only way to reliably determining default boundaries between certain significant text elements: user-perceived characters, words, and sentences.
For that, you need an external library like rivo/uniseg, which does Unicode Text Segmentation.
That will actually count "grapheme cluster", where multiple code points may be combined into one user-perceived character.
package uniseg
import (
"fmt"
"github.com/rivo/uniseg"
)
func main() {
gr := uniseg.NewGraphemes("!")
for gr.Next() {
fmt.Printf("%x ", gr.Runes())
}
// Output: [1f44d 1f3fc] [21]
}
Two graphemes, even though there are three runes (Unicode code points).
You can see other examples in "How to manipulate strings in GO to reverse them?"
? alone is one grapheme, but, from unicode to code points converter, 4 runes:
Remove border from IFrame
Either add the frameBorder attribute, or use style with border-width 0px;, or set border style equal to none.
use any one from below 3:
_x000D_
_x000D_
<iframe src="myURL" width="300" height="300" style="border-width:0px;">Browser not compatible.</iframe>_x000D_
_x000D_
<iframe src="myURL" width="300" height="300" frameborder="0">Browser not compatible.</iframe>_x000D_
_x000D_
<iframe src="myURL" width="300" height="300" style="border:none;">Browser not compatible.</iframe>
_x000D_
_x000D_
_x000D_
Convert RGB to Black & White in OpenCV
A simple way of "binarize" an image is to compare to a threshold:
For example you can compare all elements in a matrix against a value with opencv in c++
cv::Mat img = cv::imread("image.jpg", CV_LOAD_IMAGE_GRAYSCALE);
cv::Mat bw = img > 128;
In this way, all pixels in the matrix greater than 128 now are white, and these less than 128 or equals will be black
Optionally, and for me gave good results is to apply blur
cv::blur( bw, bw, cv::Size(3,3) );
Later you can save it as said before with:
cv::imwrite("image_bw.jpg", bw);
Spark SQL: apply aggregate functions to a list of columns
There are multiple ways of applying aggregate functions to multiple columns.
GroupedData
class provides a number of methods for the most common functions, including count
, max
, min
, mean
and sum
, which can be used directly as follows:
Python:
df = sqlContext.createDataFrame(
[(1.0, 0.3, 1.0), (1.0, 0.5, 0.0), (-1.0, 0.6, 0.5), (-1.0, 5.6, 0.2)],
("col1", "col2", "col3"))
df.groupBy("col1").sum()
## +----+---------+-----------------+---------+
## |col1|sum(col1)| sum(col2)|sum(col3)|
## +----+---------+-----------------+---------+
## | 1.0| 2.0| 0.8| 1.0|
## |-1.0| -2.0|6.199999999999999| 0.7|
## +----+---------+-----------------+---------+
Scala
val df = sc.parallelize(Seq(
(1.0, 0.3, 1.0), (1.0, 0.5, 0.0),
(-1.0, 0.6, 0.5), (-1.0, 5.6, 0.2))
).toDF("col1", "col2", "col3")
df.groupBy($"col1").min().show
// +----+---------+---------+---------+
// |col1|min(col1)|min(col2)|min(col3)|
// +----+---------+---------+---------+
// | 1.0| 1.0| 0.3| 0.0|
// |-1.0| -1.0| 0.6| 0.2|
// +----+---------+---------+---------+
Optionally you can pass a list of columns which should be aggregated
df.groupBy("col1").sum("col2", "col3")
You can also pass dictionary / map with columns a the keys and functions as the values:
Python
exprs = {x: "sum" for x in df.columns}
df.groupBy("col1").agg(exprs).show()
## +----+---------+
## |col1|avg(col3)|
## +----+---------+
## | 1.0| 0.5|
## |-1.0| 0.35|
## +----+---------+
Scala
val exprs = df.columns.map((_ -> "mean")).toMap
df.groupBy($"col1").agg(exprs).show()
// +----+---------+------------------+---------+
// |col1|avg(col1)| avg(col2)|avg(col3)|
// +----+---------+------------------+---------+
// | 1.0| 1.0| 0.4| 0.5|
// |-1.0| -1.0|3.0999999999999996| 0.35|
// +----+---------+------------------+---------+
Finally you can use varargs:
Python
from pyspark.sql.functions import min
exprs = [min(x) for x in df.columns]
df.groupBy("col1").agg(*exprs).show()
Scala
import org.apache.spark.sql.functions.sum
val exprs = df.columns.map(sum(_))
df.groupBy($"col1").agg(exprs.head, exprs.tail: _*)
There are some other way to achieve a similar effect but these should more than enough most of the time.
See also:
How to determine day of week by passing specific date?
Below is the two line of snippet using Java 1.8 Time API for your Requirement.
LocalDate localDate = LocalDate.of(Integer.valueOf(year),Integer.valueOf(month),Integer.valueOf(day));
String dayOfWeek = String.valueOf(localDate.getDayOfWeek());
Permutations between two lists of unequal length
The better answers to this only work for specific lengths of lists that are provided.
Here's a version that works for any lengths of input. It also makes the algorithm clear in terms of the mathematical concepts of combination and permutation.
from itertools import combinations, permutations
list1 = ['1', '2']
list2 = ['A', 'B', 'C']
num_elements = min(len(list1), len(list2))
list1_combs = list(combinations(list1, num_elements))
list2_perms = list(permutations(list2, num_elements))
result = [
tuple(zip(perm, comb))
for comb in list1_combs
for perm in list2_perms
]
for idx, ((l11, l12), (l21, l22)) in enumerate(result):
print(f'{idx}: {l11}{l12} {l21}{l22}')
This outputs:
0: A1 B2
1: A1 C2
2: B1 A2
3: B1 C2
4: C1 A2
5: C1 B2
How to delete all the rows in a table using Eloquent?
I've seen both methods been used in seed files.
// Uncomment the below to wipe the table clean before populating
DB::table('table_name')->truncate();
//or
DB::table('table_name')->delete();
Even though you can not use the first one if you want to set foreign keys.
Cannot truncate a table referenced in a foreign key constraint
So it might be a good idea to use the second one.
How to get list of dates between two dates in mysql select query
Try:
select * from
(select adddate('1970-01-01',t4.i*10000 + t3.i*1000 + t2.i*100 + t1.i*10 + t0.i) selected_date from
(select 0 i union select 1 union select 2 union select 3 union select 4 union select 5 union select 6 union select 7 union select 8 union select 9) t0,
(select 0 i union select 1 union select 2 union select 3 union select 4 union select 5 union select 6 union select 7 union select 8 union select 9) t1,
(select 0 i union select 1 union select 2 union select 3 union select 4 union select 5 union select 6 union select 7 union select 8 union select 9) t2,
(select 0 i union select 1 union select 2 union select 3 union select 4 union select 5 union select 6 union select 7 union select 8 union select 9) t3,
(select 0 i union select 1 union select 2 union select 3 union select 4 union select 5 union select 6 union select 7 union select 8 union select 9) t4) v
where selected_date between '2012-02-10' and '2012-02-15'
-for date ranges up to nearly 300 years in the future.
[Corrected following a suggested edit by UrvishAtSynapse.]
Get table name by constraint name
SELECT owner, table_name
FROM dba_constraints
WHERE constraint_name = <<your constraint name>>
will give you the name of the table. If you don't have access to the DBA_CONSTRAINTS
view, ALL_CONSTRAINTS
or USER_CONSTRAINTS
should work as well.
Best C++ Code Formatter/Beautifier
AStyle can be customized in great detail for C++ and Java (and others too)
This is a source code formatting tool.
clang-format is a powerful command line tool bundled with the clang compiler which handles even the most obscure language constructs in a coherent way.
It can be integrated with Visual Studio, Emacs, Vim (and others) and can format just the selected lines (or with git/svn to format some diff).
It can be configured with a variety of options listed here.
When using config files (named .clang-format
) styles can be per directory - the closest such file in parent directories shall be used for a particular file.
Styles can be inherited from a preset (say LLVM or Google) and can later override different options
It is used by Google and others and is production ready.
Also look at the project UniversalIndentGUI. You can experiment with several indenters using it: AStyle, Uncrustify, GreatCode, ... and select the best for you. Any of them can be run later from a command line.
Uncrustify has a lot of configurable options. You'll probably need Universal Indent GUI (in Konstantin's reply) as well to configure it.
Why can't I call a public method in another class?
It sounds like you're not instantiating your class. That's the primary reason I get the "an object reference is required" error.
MyClass myClass = new MyClass();
once you've added that line you can then call your method
myClass.myMethod();
Also, are all of your classes in the same namespace? When I was first learning c# this was a common tripping point for me.
Most efficient way to find smallest of 3 numbers Java?
If you will call min() around 1kk times with different a, b, c, then use my method:
Here only two comparisons. There is no way to calc faster :P
public static double min(double a, double b, double c) {
if (a > b) { //if true, min = b
if (b > c) { //if true, min = c
return c;
} else { //else min = b
return b;
}
} //else min = a
if (a > c) { // if true, min=c
return c;
} else {
return a;
}
}
How can I remove duplicate rows?
To Fetch Duplicate Rows:
SELECT
name, email, COUNT(*)
FROM
users
GROUP BY
name, email
HAVING COUNT(*) > 1
To Delete the Duplicate Rows:
DELETE users
WHERE rowid NOT IN
(SELECT MIN(rowid)
FROM users
GROUP BY name, email);
Request string without GET arguments
I had the same problem when I wanted a link back to homepage. I tried this and it worked:
<a href="<?php echo $_SESSION['PHP_SELF']; ?>?">
Note the question mark at the end. I believe that tells the machine stop thinking on behalf of the coder :)
How to center a Window in Java?
On Linux the code
setLocationRelativeTo(null)
Put my window to random location each time I launched it, in a multi display environment.
And the code
setLocation((Toolkit.getDefaultToolkit().getScreenSize().width - getSize().width) / 2, (Toolkit.getDefaultToolkit().getScreenSize().height - getSize().height) / 2);
"cut" the window in half with placing it to the exact center, which is between my two displays.
I used the following method to center it:
private void setWindowPosition(JFrame window, int screen)
{
GraphicsEnvironment env = GraphicsEnvironment.getLocalGraphicsEnvironment();
GraphicsDevice[] allDevices = env.getScreenDevices();
int topLeftX, topLeftY, screenX, screenY, windowPosX, windowPosY;
if (screen < allDevices.length && screen > -1)
{
topLeftX = allDevices[screen].getDefaultConfiguration().getBounds().x;
topLeftY = allDevices[screen].getDefaultConfiguration().getBounds().y;
screenX = allDevices[screen].getDefaultConfiguration().getBounds().width;
screenY = allDevices[screen].getDefaultConfiguration().getBounds().height;
}
else
{
topLeftX = allDevices[0].getDefaultConfiguration().getBounds().x;
topLeftY = allDevices[0].getDefaultConfiguration().getBounds().y;
screenX = allDevices[0].getDefaultConfiguration().getBounds().width;
screenY = allDevices[0].getDefaultConfiguration().getBounds().height;
}
windowPosX = ((screenX - window.getWidth()) / 2) + topLeftX;
windowPosY = ((screenY - window.getHeight()) / 2) + topLeftY;
window.setLocation(windowPosX, windowPosY);
}
Makes the window appear right at the center of the first display.
This is probably not the easiest solution.
Works properly on Linux, Windows and Mac.
Could not find or load main class with a Jar File
I had the same problem due to copying and pasting code from a Microsoft Word Document. Seems there was a slightly different type of dash -
character used, when I replaced the longer dash character with the correct -
the program executed properly
Detect Route Change with react-router
I came across this question as I was attempting to focus the ChromeVox screen reader to the top of the "screen" after navigating to a new screen in a React single page app. Basically trying to emulate what would happen if this page was loaded by following a link to a new server-rendered web page.
This solution doesn't require any listeners, it uses withRouter()
and the componentDidUpdate()
lifecycle method to trigger a click to focus ChromeVox on the desired element when navigating to a new url path.
Implementation
I created a "Screen" component which is wrapped around the react-router switch tag which contains all the apps screens.
<Screen>
<Switch>
... add <Route> for each screen here...
</Switch>
</Screen>
Screen.tsx
Component
Note: This component uses React + TypeScript
import React from 'react'
import { RouteComponentProps, withRouter } from 'react-router'
class Screen extends React.Component<RouteComponentProps> {
public screen = React.createRef<HTMLDivElement>()
public componentDidUpdate = (prevProps: RouteComponentProps) => {
if (this.props.location.pathname !== prevProps.location.pathname) {
// Hack: setTimeout delays click until end of current
// event loop to ensure new screen has mounted.
window.setTimeout(() => {
this.screen.current!.click()
}, 0)
}
}
public render() {
return <div ref={this.screen}>{this.props.children}</div>
}
}
export default withRouter(Screen)
I had tried using focus()
instead of click()
, but click causes ChromeVox to stop reading whatever it is currently reading and start again where I tell it to start.
Advanced note: In this solution, the navigation <nav>
which inside the Screen component and rendered after the <main>
content is visually positioned above the main
using css order: -1;
. So in pseudo code:
<Screen style={{ display: 'flex' }}>
<main>
<nav style={{ order: -1 }}>
<Screen>
If you have any thoughts, comments, or tips about this solution, please add a comment.
How to loop through a plain JavaScript object with the objects as members?
The problem with this
for (var key in validation_messages) {
var obj = validation_messages[key];
for (var prop in obj) {
alert(prop + " = " + obj[prop]);
}
}
is that you’ll also loop through the primitive object's prototype.
With this one you will avoid it:
for (var key in validation_messages) {
if (validation_messages.hasOwnProperty(key)) {
var obj = validation_messages[key];
for (var prop in obj) {
if (obj.hasOwnProperty(prop)) {
alert(prop + " = " + obj[prop]);
}
}
}
}
What is the logic behind the "using" keyword in C++?
In C++11, the using
keyword when used for type alias
is identical to typedef
.
7.1.3.2
A typedef-name can also be introduced by an alias-declaration. The
identifier following the using keyword becomes a typedef-name and the
optional attribute-specifier-seq following the identifier appertains
to that typedef-name. It has the same semantics as if it were
introduced by the typedef specifier. In particular, it does not define
a new type and it shall not appear in the type-id.
Bjarne Stroustrup provides a practical example:
typedef void (*PFD)(double); // C style typedef to make `PFD` a pointer to a function returning void and accepting double
using PF = void (*)(double); // `using`-based equivalent of the typedef above
using P = [](double)->void; // using plus suffix return type, syntax error
using P = auto(double)->void // Fixed thanks to DyP
Pre-C++11, the using
keyword can bring member functions into scope. In C++11, you can now do this for constructors (another Bjarne Stroustrup example):
class Derived : public Base {
public:
using Base::f; // lift Base's f into Derived's scope -- works in C++98
void f(char); // provide a new f
void f(int); // prefer this f to Base::f(int)
using Base::Base; // lift Base constructors Derived's scope -- C++11 only
Derived(char); // provide a new constructor
Derived(int); // prefer this constructor to Base::Base(int)
// ...
};
Ben Voight provides a pretty good reason behind the rationale of not introducing a new keyword or new syntax. The standard wants to avoid breaking old code as much as possible. This is why in proposal documents you will see sections like Impact on the Standard
, Design decisions
, and how they might affect older code. There are situations when a proposal seems like a really good idea but might not have traction because it would be too difficult to implement, too confusing, or would contradict old code.
Here is an old paper from 2003 n1449. The rationale seems to be related to templates. Warning: there may be typos due to copying over from PDF.
First let’s consider a toy example:
template <typename T>
class MyAlloc {/*...*/};
template <typename T, class A>
class MyVector {/*...*/};
template <typename T>
struct Vec {
typedef MyVector<T, MyAlloc<T> > type;
};
Vec<int>::type p; // sample usage
The fundamental problem with this idiom, and the main motivating fact
for this proposal, is that the idiom causes the template parameters to
appear in non-deducible context. That is, it will not be possible to
call the function foo below without explicitly specifying template
arguments.
template <typename T> void foo (Vec<T>::type&);
So, the syntax is somewhat ugly. We would rather avoid the nested ::type
We’d prefer something like the following:
template <typename T>
using Vec = MyVector<T, MyAlloc<T> >; //defined in section 2 below
Vec<int> p; // sample usage
Note that we specifically avoid the term “typedef template” and
introduce the new syntax involving the pair “using” and “=” to help avoid
confusion: we are not defining any types here, we are introducing a
synonym (i.e. alias) for an abstraction of a type-id (i.e. type
expression) involving template parameters. If the template parameters
are used in deducible contexts in the type expression then whenever
the template alias is used to form a template-id, the values of the
corresponding template parameters can be deduced – more on this will
follow. In any case, it is now possible to write generic functions
which operate on Vec<T>
in deducible context, and the syntax is
improved as well. For example we could rewrite foo as:
template <typename T> void foo (Vec<T>&);
We underscore here that one of the primary reasons for proposing
template aliases was so that argument deduction and the call to foo(p)
will succeed.
The follow-up paper n1489 explains why using
instead of using typedef
:
It has been suggested to (re)use the keyword typedef — as done in the
paper [4] — to introduce template aliases:
template<class T>
typedef std::vector<T, MyAllocator<T> > Vec;
That notation has the advantage of using a keyword already known to
introduce a type alias. However, it also displays several
disavantages among which the confusion of using a keyword known to
introduce an alias for a type-name in a context where the alias does
not designate a type, but a template; Vec
is not an alias for a
type, and should not be taken for a typedef-name. The name Vec
is a
name for the family std::vector< [bullet] , MyAllocator< [bullet] > >
– where the bullet is a placeholder for a type-name. Consequently we
do not propose the “typedef” syntax. On the other hand the sentence
template<class T>
using Vec = std::vector<T, MyAllocator<T> >;
can be read/interpreted as: from now on, I’ll be using Vec<T>
as a
synonym for std::vector<T, MyAllocator<T> >
. With that reading, the
new syntax for aliasing seems reasonably logical.
I think the important distinction is made here, aliases instead of types. Another quote from the same document:
An alias-declaration is a declaration, and not a definition. An alias-
declaration introduces a name into a declarative region as an alias
for the type designated by the right-hand-side of the declaration. The
core of this proposal concerns itself with type name aliases, but the
notation can obviously be generalized to provide alternate spellings
of namespace-aliasing or naming set of overloaded functions (see ?
2.3 for further discussion). [My note: That section discusses what that syntax can look like and reasons why it isn't part of the proposal.] It may be noted that the grammar production alias-declaration is acceptable anywhere a typedef
declaration or a namespace-alias-definition is acceptable.
Summary, for the role of using
:
- template aliases (or template typedefs, the former is preferred namewise)
- namespace aliases (i.e.,
namespace PO = boost::program_options
and using PO = ...
equivalent)
- the document says
A typedef declaration can be viewed as a special case of non-template alias-declaration
. It's an aesthetic change, and is considered identical in this case.
- bringing something into scope (for example,
namespace std
into the global scope), member functions, inheriting constructors
It cannot be used for:
int i;
using r = i; // compile-error
Instead do:
using r = decltype(i);
Naming a set of overloads.
// bring cos into scope
using std::cos;
// invalid syntax
using std::cos(double);
// not allowed, instead use Bjarne Stroustrup function pointer alias example
using test = std::cos(double);
Visibility of global variables in imported modules
A function uses the globals of the module it's defined in. Instead of setting a = 3
, for example, you should be setting module1.a = 3
. So, if you want cur
available as a global in utilities_module
, set utilities_module.cur
.
A better solution: don't use globals. Pass the variables you need into the functions that need it, or create a class to bundle all the data together, and pass it when initializing the instance.
Connect to mysql on Amazon EC2 from a remote server
I went through all the previous answers (and answers to similar questions) without success, so here is what finally worked for me. The key step was to explicitly grant privileges on the mysql server to a local user (for the server), but with my local IP appended to it (myuser@*.*.*.*
). The complete step by step solution is as follows:
Comment out the bind_address
line in /etc/mysql/my.cnf
at the server (i.e. the EC2 Instance). I suppose
bind_address=0.0.0.0
would also work, but it's not needed as
others have mentioned.
Add a rule (as others have mentioned too) for MYSQL to the EC2 instance's security group with port 3306 and either My IP
or Anywhere
as Source. Both work fine after following all the steps.
Create a new user myuser
with limited privileges to one particular
database mydb
(basically following the instructions in this Amazon tutorial):
$EC2prompt> mysql -u root -p
[...omitted output...]
mysql> CREATE USER 'myuser'@'localhost' IDENTIFIED BY 'your_strong_password';
mysql> GRANT ALL PRIVILEGES ON 'mydb'.* TO 'myuser'@'localhost';`
Here's the key step, without which my local address was refused when attempting a remote connection (ERROR 1130 (HY000): Host '*.*.*.23' is not allowed to connect to this MySQL server)
:
mysql> GRANT ALL PRIVILEGES ON 'mydb'.* TO 'myuser'@'*.*.*.23';
mysql> FLUSH PRIVILEGES;`
(replace '*.*.*.23'
by your local IP address)
For good measure, I exited mysql to the shell and restarted the msyql server:
$EC2prompt> sudo service mysql restart
After these steps, I was able to happily connect from my computer with:
$localprompt> mysql -h myinstancename.amazonaws.com -P 3306 -u myuser -p
(replace myinstancename.amazonaws.com
by the public address of your EC2 instance)
How to change row color in datagridview?
This is my solution to change color to dataGridView with bindingDataSource:
private void dataGridViewECO_DataBindingComplete(object sender, DataGridViewBindingCompleteEventArgs e)
{
if (e.ListChangedType != ListChangedType.ItemDeleted)
{
DataGridViewCellStyle green = this.dataGridViewECO.DefaultCellStyle.Clone();
green.BackColor = Color.Green;
DataGridViewCellStyle gray = this.dataGridViewECO.DefaultCellStyle.Clone();
gray.BackColor = Color.LightGray;
foreach (DataGridViewRow r in this.dataGridViewECO.Rows)
{
if (r.Cells[8].Value != null)
{
String stato = r.Cells[8].Value.ToString();
if (!" Open ".Equals(stato))
{
r.DefaultCellStyle = gray;
}
else
{
r.DefaultCellStyle = green;
}
}
}
}
}
Finding a substring within a list in Python
I'd just use a simple regex, you can do something like this
import re
old_list = ['abc123', 'def456', 'ghi789']
new_list = [x for x in old_list if re.search('abc', x)]
for item in new_list:
print item
In ASP.NET MVC: All possible ways to call Controller Action Method from a Razor View
Method 1 : Using jQuery Ajax Get call (partial page update).
Suitable for when you need to retrieve jSon data from database.
Controller's Action Method
[HttpGet]
public ActionResult Foo(string id)
{
var person = Something.GetPersonByID(id);
return Json(person, JsonRequestBehavior.AllowGet);
}
Jquery GET
function getPerson(id) {
$.ajax({
url: '@Url.Action("Foo", "SomeController")',
type: 'GET',
dataType: 'json',
// we set cache: false because GET requests are often cached by browsers
// IE is particularly aggressive in that respect
cache: false,
data: { id: id },
success: function(person) {
$('#FirstName').val(person.FirstName);
$('#LastName').val(person.LastName);
}
});
}
Person class
public class Person
{
public string FirstName { get; set; }
public string LastName { get; set; }
}
Method 2 : Using jQuery Ajax Post call (partial page update).
Suitable for when you need to do partial page post data into database.
Post method is also same like above just replace [HttpPost]
on Action method and type as post
for jquery method.
For more information check Posting JSON Data to MVC Controllers Here
Method 3 : As a Form post scenario (full page update).
Suitable for when you need to save or update data into database.
View
@using (Html.BeginForm("SaveData","ControllerName", FormMethod.Post))
{
@Html.TextBoxFor(model => m.Text)
<input type="submit" value="Save" />
}
Action Method
[HttpPost]
public ActionResult SaveData(FormCollection form)
{
// Get movie to update
return View();
}
Method 4 : As a Form Get scenario (full page update).
Suitable for when you need to Get data from database
Get method also same like above just replace [HttpGet]
on Action method and FormMethod.Get
for View's form method.
I hope this will help to you.
Cannot ping AWS EC2 instance
By default EC2 is secured by AWS Security Group (A service found in EC2 and VPC). Security Group by default are disallowing Any ICMP request which includes the ping. To allow it:
Goto: AWS EC2 Instance
Locate: The Security Group bind to that instance (It's possible to have multiple security group)
Check: Inbound Rules for Protocol (ICMP) Port (0 - 65535) if it's not present you can add it and allow it on your specified source IP or Another Security Group.
How to get the fragment instance from the FragmentActivity?
To get the fragment instance in a class that extends FragmentActivity:
MyclassFragment instanceFragment=
(MyclassFragment)getSupportFragmentManager().findFragmentById(R.id.idFragment);
To get the fragment instance in a class that extends Fragment:
MyclassFragment instanceFragment =
(MyclassFragment)getFragmentManager().findFragmentById(R.id.idFragment);
How can I create and style a div using JavaScript?
Here's one solution that I'd use:
var div = '<div id="yourId" class="yourClass" yourAttribute="yourAttributeValue">blah</div>';
If you wanted the attribute and/or attribute values to be based on variables:
var id = "hello";
var classAttr = "class";
var div = '<div id='+id+' '+classAttr+'="world" >Blah</div>';
Then, to append to the body:
document.getElementsByTagName("body").innerHTML = div;
Easy as pie.
How to POST a JSON object to a JAX-RS service
I faced the same 415
http error when sending objects, serialized into JSON, via PUT/PUSH requests to my JAX-rs services, in other words my server was not able to de-serialize the objects from JSON.
In my case, the server was able to serialize successfully the same objects in JSON when sending them into its responses.
As mentioned in the other responses I have correctly set the Accept
and Content-Type
headers to application/json
, but it doesn't suffice.
Solution
I simply forgot a default constructor with no parameters for my DTO objects. Yes this is the same reasoning behind @Entity objects, you need a constructor with no parameters for the ORM to instantiate objects and populate the fields later.
Adding the constructor with no parameters to my DTO objects solved my issue.
Here follows an example that resembles my code:
Wrong
@XmlRootElement
@XmlAccessorType(XmlAccessType.FIELD)
public class NumberDTO {
public NumberDTO(Number number) {
this.number = number;
}
private Number number;
public Number getNumber() {
return number;
}
public void setNumber(Number string) {
this.number = string;
}
}
Right
@XmlRootElement
@XmlAccessorType(XmlAccessType.FIELD)
public class NumberDTO {
public NumberDTO() {
}
public NumberDTO(Number number) {
this.number = number;
}
private Number number;
public Number getNumber() {
return number;
}
public void setNumber(Number string) {
this.number = string;
}
}
I lost hours, I hope this'll save yours ;-)
Execute action when back bar button of UINavigationController is pressed
override public func viewDidLoad() {
super.viewDidLoad()
self.navigationController?.navigationBar.topItem?.title = GlobalVariables.selectedMainIconName
let image = UIImage(named: "back-btn")
image = image?.imageWithRenderingMode(UIImageRenderingMode.AlwaysOriginal)
self.navigationItem.leftBarButtonItem = UIBarButtonItem(image: image, style: UIBarButtonItemStyle.Plain, target: self, action: #selector(Current[enter image description here][1]ViewController.back) )
}
func back() {
self.navigationController?.popToViewController( self.navigationController!.viewControllers[ self.navigationController!.viewControllers.count - 2 ], animated: true)
}
pypi UserWarning: Unknown distribution option: 'install_requires'
python setup.py
uses distutils which doesn't support install_requires. setuptools does, also distribute (its successor), and pip (which uses either) do. But you actually have to use them. I.e. call setuptools through the easy_install
command or pip install
.
Another way is to import setup from setuptools in your setup.py, but this not standard and makes everybody wanting to use your package have to have setuptools installed.
How do I auto-hide placeholder text upon focus using css or jquery?
have you tried placeholder attr?
<input id ="myID" type="text" placeholder="enter your text " />
-EDIT-
I see, try this then:
$(function () {
$('#myId').data('holder', $('#myId').attr('placeholder'));
$('#myId').focusin(function () {
$(this).attr('placeholder', '');
});
$('#myId').focusout(function () {
$(this).attr('placeholder', $(this).data('holder'));
});
});
Test: http://jsfiddle.net/mPLFf/4/
-EDIT-
Actually, since placeholder should be used to describe the value, not the name of the input. I suggest the following alternative
html:
<label class="overlabel">
<span>First Name</span>
<input name="first_name" type="text" />
</label>
javascript:
$('.overlabel').each(function () {
var $this = $(this);
var field = $this.find('[type=text], [type=file], [type=email], [type=password], textarea');
var span = $(this).find('> span');
var onBlur = function () {
if ($.trim(field.val()) == '') {
field.val('');
span.fadeIn(100);
} else {
span.fadeTo(100, 0);
}
};
field.focus(function () {
span.fadeOut(100);
}).blur(onBlur);
onBlur();
});
css:
.overlabel {
border: 0.1em solid;
color: #aaa;
position: relative;
display: inline-block;
vertical-align: middle;
min-height: 2.2em;
}
.overlabel span {
position: absolute;
left: 0;
top: 0;
white-space: nowrap;
overflow: hidden;
text-overflow: ellipsis;
}
.overlabel span, .overlabel input {
text-align: left;
font-size: 1em;
line-height: 2em;
padding: 0 0.5em;
margin: 0;
background: transparent;
-webkit-appearance: none; /* prevent ios styling */
border-width: 0;
width: 100%;
outline: 0;
}
Test:
http://jsfiddle.net/kwynwrcf/
Detecting iOS orientation change instantly
For my case handling UIDeviceOrientationDidChangeNotification
was not good solution as it is called more frequent and UIDeviceOrientation
is not always equal to UIInterfaceOrientation
because of (FaceDown, FaceUp).
I handle it using UIApplicationDidChangeStatusBarOrientationNotification
:
//To add the notification
[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(didChangeOrientation:)
//to remove the
[[NSNotificationCenter defaultCenter]removeObserver:self name:UIDeviceOrientationDidChangeNotification object:nil];
...
- (void)didChangeOrientation:(NSNotification *)notification
{
UIInterfaceOrientation orientation = [UIApplication sharedApplication].statusBarOrientation;
if (UIInterfaceOrientationIsLandscape(orientation)) {
NSLog(@"Landscape");
}
else {
NSLog(@"Portrait");
}
}
Changing background color of ListView items on Android
The best tutorial on this can be found here.
Key sections:
- Surely call
view.setSelected(true)
in onItemClick
, otherwise the you can't see the selected item background
- Preserve the order of states in your selector otherwise you'll see unpredictable behavior in background colors (
state_selected
followed by state_pressed
)
How to pass all arguments passed to my bash script to a function of mine?
Here's a simple script:
#!/bin/bash
args=("$@")
echo Number of arguments: $#
echo 1st argument: ${args[0]}
echo 2nd argument: ${args[1]}
$#
is the number of arguments received by the script. I find easier to access them using an array: the args=("$@")
line puts all the arguments in the args
array. To access them use ${args[index]}
.
How to split data into training/testing sets using sample function
It can be easily done by:
set.seed(101) # Set Seed so that same sample can be reproduced in future also
# Now Selecting 75% of data as sample from total 'n' rows of the data
sample <- sample.int(n = nrow(data), size = floor(.75*nrow(data)), replace = F)
train <- data[sample, ]
test <- data[-sample, ]
By using caTools package:
require(caTools)
set.seed(101)
sample = sample.split(data$anycolumn, SplitRatio = .75)
train = subset(data, sample == TRUE)
test = subset(data, sample == FALSE)
How do I create a constant in Python?
In my case, I needed immutable bytearrays for an implementation of a crypto library containing many literal numbers I wanted to ensure were constant.
This answer works but attempted reassignment of bytearray elements does not raise an error.
def const(func):
'''implement const decorator'''
def fset(self, val):
'''attempting to set a const raises `ConstError`'''
class ConstError(TypeError):
'''special exception for const reassignment'''
pass
raise ConstError
def fget(self):
'''get a const'''
return func()
return property(fget, fset)
class Consts(object):
'''contain all constants'''
@const
def C1():
'''reassignment to C1 fails silently'''
return bytearray.fromhex('deadbeef')
@const
def pi():
'''is immutable'''
return 3.141592653589793
Constants are immutable, but constant bytearray assignment fails silently:
>>> c = Consts()
>>> c.pi = 6.283185307179586 # (https://en.wikipedia.org/wiki/Tau_(2%CF%80))
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "consts.py", line 9, in fset
raise ConstError
__main__.ConstError
>>> c.C1[0] = 0
>>> c.C1[0]
222
>>> c.C1
bytearray(b'\xde\xad\xbe\xef')
A more powerful, simple, and perhaps even more 'pythonic' approach involves the use of memoryview objects (buffer objects in <= python-2.6).
import sys
PY_VER = sys.version.split()[0].split('.')
if int(PY_VER[0]) == 2:
if int(PY_VER[1]) < 6:
raise NotImplementedError
elif int(PY_VER[1]) == 6:
memoryview = buffer
class ConstArray(object):
'''represent a constant bytearray'''
def __init__(self, init):
'''
create a hidden bytearray and expose a memoryview of that bytearray for
read-only use
'''
if int(PY_VER[1]) == 6:
self.__array = bytearray(init.decode('hex'))
else:
self.__array = bytearray.fromhex(init)
self.array = memoryview(self.__array)
def __str__(self):
return str(self.__array)
def __getitem__(self, *args, **kwargs):
return self.array.__getitem__(*args, **kwargs)
ConstArray item assignment is a TypeError
:
>>> C1 = ConstArray('deadbeef')
>>> C1[0] = 0
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
TypeError: 'ConstArray' object does not support item assignment
>>> C1[0]
222
Callback functions in Java
A method is not (yet) a first-class object in Java; you can't pass a function pointer as a callback. Instead, create an object (which usually implements an interface) that contains the method you need and pass that.
Proposals for closures in Java—which would provide the behavior you are looking for—have been made, but none will be included in the upcoming Java 7 release.
Disallow Twitter Bootstrap modal window from closing
If you already have initialized the modal window, then you may want to reset the options with $('#myModal').removeData("modal").modal({backdrop: 'static', keyboard: false})
to make sure it will apply the new options.
Default property value in React component using TypeScript
For the functional component, I would rather keep the props
argument, so here is my solution:
interface Props {
foo: string;
bar?: number;
}
// IMPORTANT!, defaultProps is of type {bar: number} rather than Partial<Props>!
const defaultProps = {
bar: 1
}
// externalProps is of type Props
const FooComponent = exposedProps => {
// props works like type Required<Props> now!
const props = Object.assign(defaultProps, exposedProps);
return ...
}
FooComponent.defaultProps = defaultProps;
How do you revert to a specific tag in Git?
Git tags are just pointers to the commit. So you use them the same way as you do HEAD, branch names or commit sha hashes. You can use tags with any git command that accepts commit/revision arguments. You can try it with git rev-parse tagname
to display the commit it points to.
In your case you have at least these two alternatives:
Reset the current branch to specific tag:
git reset --hard tagname
Generate revert commit on top to get you to the state of the tag:
git revert tag
This might introduce some conflicts if you have merge commits though.
Display a RecyclerView in Fragment
You should retrieve RecyclerView
in a Fragment
after inflating core View using that View. Perhaps it can't find your recycler because it's not part of Activity
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
final View view = inflater.inflate(R.layout.fragment_artist_tracks, container, false);
final FragmentActivity c = getActivity();
final RecyclerView recyclerView = (RecyclerView) view.findViewById(R.id.recyclerView);
LinearLayoutManager layoutManager = new LinearLayoutManager(c);
recyclerView.setLayoutManager(layoutManager);
new Thread(new Runnable() {
@Override
public void run() {
final RecyclerAdapter adapter = new RecyclerAdapter(c);
c.runOnUiThread(new Runnable() {
@Override
public void run() {
recyclerView.setAdapter(adapter);
}
});
}
}).start();
return view;
}
How to install the Raspberry Pi cross compiler on my Linux host machine?
The initial question has been posted quite some time ago and in the meantime Debian has made huge headway in the area of multiarch support.
Multiarch is a great achievement for cross compilation!
In a nutshell the following steps are required to leverage multiarch for Raspbian Jessie cross compilation:
- On your Ubuntu host install Debian Jessie amd64 within a chroot or a LXC container.
- Enable the foreign architecture armhf.
- Install the cross compiler from the emdebian tools repository.
- Tweak the cross compiler (it would generate code for ARMv7-A by default) by writing a custom gcc specs file.
- Install armhf libraries (libstdc++ etc.) from the Raspbian repository.
- Build your source code.
Since this is a lot of work I have automated the above setup. You can read about it here:
Cross Compiling for Raspbian
how to add value to a tuple?
list_of_tuples = [('1', '2', '3', '4'),
('2', '3', '4', '5'),
('3', '4', '5', '6'),
('4', '5', '6', '7')]
def mod_tuples(list_of_tuples):
for i in range(0, len(list_of_tuples)):
addition = ''
for x in list_of_tuples[i]:
addition = addition + x
list_of_tuples[i] = list_of_tuples[i] + (addition,)
return list_of_tuples
# check:
print mod_tuples(list_of_tuples)
Can I change the viewport meta tag in mobile safari on the fly?
in your <head>
<meta id="viewport"
name="viewport"
content="width=1024, height=768, initial-scale=0, minimum-scale=0.25" />
somewhere in your javascript
document.getElementById("viewport").setAttribute("content",
"initial-scale=0.5; maximum-scale=1.0; user-scalable=0;");
... but good luck with tweaking it for your device, fiddling for hours... and i'm still not there!
source
Count character occurrences in a string in C++
Pseudocode:
count = 0
For each character c in string s
Check if c equals '_'
If yes, increase count
EDIT: C++ example code:
int count_underscores(string s) {
int count = 0;
for (int i = 0; i < s.size(); i++)
if (s[i] == '_') count++;
return count;
}
Note that this is code to use together with std::string
, if you're using char*
, replace s.size()
with strlen(s)
.
Also note: I can understand you want something "as small as possible", but I'd suggest you to use this solution instead. As you see you can use a function to encapsulate the code for you so you won't have to write out the for
loop everytime, but can just use count_underscores("my_string_")
in the rest of your code. Using advanced C++ algorithms is certainly possible here, but I think it's overkill.
Deserializing JSON Object Array with Json.net
Further modification from JC_VA, take what he has, and replace the MyModelConverter with...
public class MyModelConverter : JsonConverter
{
//objectType is the type as specified for List<myModel> (i.e. myModel)
public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer)
{
var token = JToken.Load(reader); //json from myModelList > model
var list = Activator.CreateInstance(objectType) as System.Collections.IList; // new list to return
var itemType = objectType.GenericTypeArguments[0]; // type of the list (myModel)
if (token.Type.ToString() == "Object") //Object
{
var child = token.Children();
var newObject = Activator.CreateInstance(itemType);
serializer.Populate(token.CreateReader(), newObject);
list.Add(newObject);
}
else //Array
{
foreach (var child in token.Children())
{
var newObject = Activator.CreateInstance(itemType);
serializer.Populate(child.CreateReader(), newObject);
list.Add(newObject);
}
}
return list;
}
public override bool CanConvert(Type objectType)
{
return objectType.IsGenericType && (objectType.GetGenericTypeDefinition() == typeof(List<>));
}
public override bool CanWrite => false;
public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer) => throw new NotImplementedException();
}
This should work for json that is either
myModelList{
model: [{ ... object ... }]
}
or
myModelList{
model: { ... object ... }
}
they will both end up being parsed as if they were
myModelList{
model: [{ ... object ... }]
}
iOS Safari – How to disable overscroll but allow scrollable divs to scroll normally?
Best solution to this is css/html:
Make a div to wrap your elements in, if you dont have it already
And set it to position fixed and overflow hidden. Optional, set height and width to 100% if you want it to fill the whole screen and nothing but the whole screen
_x000D_
_x000D_
#wrapper{_x000D_
height: 100%;_x000D_
width: 100%;_x000D_
position: fixed;_x000D_
overflow: hidden;_x000D_
}
_x000D_
<div id="wrapper">_x000D_
<p>All</p>_x000D_
<p>Your</p>_x000D_
<p>Elements</p>_x000D_
</div>
_x000D_
_x000D_
_x000D_
Can I set enum start value in Java?
If you use very big enum types then, following can be useful;
public enum deneme {
UPDATE, UPDATE_FAILED;
private static Map<Integer, deneme> ss = new TreeMap<Integer,deneme>();
private static final int START_VALUE = 100;
private int value;
static {
for(int i=0;i<values().length;i++)
{
values()[i].value = START_VALUE + i;
ss.put(values()[i].value, values()[i]);
}
}
public static deneme fromInt(int i) {
return ss.get(i);
}
public int value() {
return value;
}
}
How do I enable C++11 in gcc?
I think you could do it using a specs file.
Under MinGW you could run
gcc -dumpspecs > specs
Where it says
*cpp:
%{posix:-D_POSIX_SOURCE} %{mthreads:-D_MT}
You change it to
*cpp:
%{posix:-D_POSIX_SOURCE} %{mthreads:-D_MT} -std=c++11
And then place it in
/mingw/lib/gcc/mingw32/<version>/specs
I'm sure you could do the same without a MinGW build. Not sure where to place the specs file though.
The folder is probably either /gcc/lib/ or /gcc/.
Docker: Copying files from Docker container to host
Mount a volume, copy the artifacts, adjust owner id and group id:
mkdir artifacts
docker run -i --rm -v ${PWD}/artifacts:/mnt/artifacts centos:6 /bin/bash << COMMANDS
ls -la > /mnt/artifacts/ls.txt
echo Changing owner from \$(id -u):\$(id -g) to $(id -u):$(id -g)
chown -R $(id -u):$(id -g) /mnt/artifacts
COMMANDS
EDIT: Note that some of the commands like $(id -u)
are backslashed and will therefore be processed within the container, while the ones that are not backslashed will be processed by the shell being run in the host machine BEFORE the commands are sent to the container.
Java SimpleDateFormat for time zone with a colon separator?
Since an example of Apache FastDateFormat(click for the documentations of versions:2.6and3.5) is missing here, I am adding one for those who may need it. The key here is the pattern ZZ
(2 capital Z
s).
import java.text.ParseException
import java.util.Date;
import org.apache.commons.lang3.time.FastDateFormat;
public class DateFormatTest throws ParseException {
public static void main(String[] args) {
String stringDateFormat = "yyyy-MM-dd'T'HH:mm:ssZZ";
FastDateFormat fastDateFormat = FastDateFormat.getInstance(stringDateFormat);
System.out.println("Date formatted into String:");
System.out.println(fastDateFormat.format(new Date()));
String stringFormattedDate = "2016-11-22T14:30:14+05:30";
System.out.println("String parsed into Date:");
System.out.println(fastDateFormat.parse(stringFormattedDate));
}
}
Here is the output of the code:
Date formatted into String:
2016-11-22T14:52:17+05:30
String parsed into Date:
Tue Nov 22 14:30:14 IST 2016
Note: The above code is of Apache Commons' lang3. The class org.apache.commons.lang.time.FastDateFormat
does not support parsing, and it supports only formatting. For example, the output of the following code:
import java.text.ParseException;
import java.util.Date;
import org.apache.commons.lang.time.FastDateFormat;
public class DateFormatTest {
public static void main(String[] args) throws ParseException {
String stringDateFormat = "yyyy-MM-dd'T'HH:mm:ssZZ";
FastDateFormat fastDateFormat = FastDateFormat.getInstance(stringDateFormat);
System.out.println("Date formatted into String:");
System.out.println(fastDateFormat.format(new Date()));
String stringFormattedDate = "2016-11-22T14:30:14+05:30";
System.out.println("String parsed into Date:");
System.out.println(fastDateFormat.parseObject(stringFormattedDate));
}
}
will be this:
Date formatted into String:
2016-11-22T14:55:56+05:30
String parsed into Date:
Exception in thread "main" java.text.ParseException: Format.parseObject(String) failed
at java.text.Format.parseObject(Format.java:228)
at DateFormatTest.main(DateFormatTest.java:12)
How should I call 3 functions in order to execute them one after the other?
Since you tagged it with javascript, I would go with a timer control since your function names are 3, 5, and 8 seconds. So start your timer, 3 seconds in, call the first, 5 seconds in call the second, 8 seconds in call the third, then when it's done, stop the timer.
Normally in Javascript what you have is correct for the functions are running one after another, but since it looks like you're trying to do timed animation, a timer would be your best bet.
Download files in laravel using Response::download
HTML link click
<a class="download" href="{{route('project.download',$post->id)}}">DOWNLOAD</a>
// Route
Route::group(['middleware'=>['auth']], function(){
Route::get('file-download/{id}', 'PostController@downloadproject')->name('project.download');
});
public function downloadproject($id) {
$book_cover = Post::where('id', $id)->firstOrFail();
$path = public_path(). '/storage/uploads/zip/'. $book_cover->zip;
return response()->download($path, $book_cover
->original_filename, ['Content-Type' => $book_cover->mime]);
}
Changing CSS for last <li>
:last-child is CSS3 and has no IE support while :first-child is CSS2, I believe the following is the safe way to implement it using jquery
$('li').last().addClass('someClass');
How do I delete files programmatically on Android?
File file=new File(getFilePath(imageUri.getValue()));
boolean b= file.delete();
not working in my case. The issue has been resolved by using below code-
ContentResolver contentResolver = getContentResolver ();
contentResolver.delete (uriDelete,null ,null );
How can I check if a value is of type Integer?
If you have a double/float/floating point number and want to see if it's an integer.
public boolean isDoubleInt(double d)
{
//select a "tolerance range" for being an integer
double TOLERANCE = 1E-5;
//do not use (int)d, due to weird floating point conversions!
return Math.abs(Math.floor(d) - d) < TOLERANCE;
}
If you have a string and want to see if it's an integer. Preferably, don't throw out the Integer.valueOf()
result:
public boolean isStringInt(String s)
{
try
{
Integer.parseInt(s);
return true;
} catch (NumberFormatException ex)
{
return false;
}
}
If you want to see if something is an Integer object (and hence wraps an int
):
public boolean isObjectInteger(Object o)
{
return o instanceof Integer;
}
Python MYSQL update statement
@Esteban Küber is absolutely right.
Maybe one additional hint for bloody beginners like me.
If you speciify the variables with %s, you have to follow this principle
for EVERY input value, which means for the SET-variables as well as for the WHERE-variables.
Otherwise, you will have to face a termination message like
'You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near '%s WHERE'
First char to upper case
userIdeaUC = userIdea.substring(0, 1).toUpperCase() + userIdea.length() > 1 ? userIdea.substring(1) : "";
or
userIdeaUC = userIdea.substring(0, 1).toUpperCase();
if(userIdea.length() > 1)
userIdeaUC += userIdea.substring(1);
Can I force a page break in HTML printing?
I needed a page break after every 3rd row while we use print command on browser.
I added
<div style='page-break-before: always;'></div>
after every 3rd row and my parent div have display: flex;
so I removed display: flex;
and it was working as I want.
Remove NA values from a vector
I ran a quick benchmark comparing the two base
approaches and it turns out that x[!is.na(x)]
is faster than na.omit
. User qwr
suggested I try purrr::dicard
also - this turned out to be massively slower (though I'll happily take comments on my implementation & test!)
microbenchmark::microbenchmark(
purrr::map(airquality,function(x) {x[!is.na(x)]}),
purrr::map(airquality,na.omit),
purrr::map(airquality, ~purrr::discard(.x, .p = is.na)),
times = 1e6)
Unit: microseconds
expr min lq mean median uq max neval cld
purrr::map(airquality, function(x) { x[!is.na(x)] }) 66.8 75.9 130.5643 86.2 131.80 541125.5 1e+06 a
purrr::map(airquality, na.omit) 95.7 107.4 185.5108 129.3 190.50 534795.5 1e+06 b
purrr::map(airquality, ~purrr::discard(.x, .p = is.na)) 3391.7 3648.6 5615.8965 4079.7 6486.45 1121975.4 1e+06 c
For reference, here's the original test of x[!is.na(x)]
vs na.omit
:
microbenchmark::microbenchmark(
purrr::map(airquality,function(x) {x[!is.na(x)]}),
purrr::map(airquality,na.omit),
times = 1000000)
Unit: microseconds
expr min lq mean median uq max neval cld
map(airquality, function(x) { x[!is.na(x)] }) 53.0 56.6 86.48231 58.1 64.8 414195.2 1e+06 a
map(airquality, na.omit) 85.3 90.4 134.49964 92.5 104.9 348352.8 1e+06 b
PHP: how can I get file creation date?
Unfortunately if you are running on linux you cannot access the information as only the last modified date is stored.
It does slightly depend on your filesystem tho. I know that ext2 and ext3 do not support creation time but I think that ext4 does.
Error while installing json gem 'mkmf.rb can't find header files for ruby'
On Mac 10.14, the header files don't seem to be installed in the correct place. Rather than changing paths like the other fixes, I was able to just run this:
open /Library/Developer/CommandLineTools/Packages/macOS_SDK_headers_for_macOS_10.14.pkg
Follow the instructions and it resolved this problem for me.
HTML form do some "action" when hit submit button
index.html
<!DOCTYPE html>
<html>
<body>
<form action="submit.php" method="POST">
First name: <input type="text" name="firstname" /><br /><br />
Last name: <input type="text" name="lastname" /><br />
<input type="submit" value="Submit" />
</form>
</body>
</html>
After that one more file which page you want to display after pressing the submit button
submit.php
<html>
<body>
Your First Name is - <?php echo $_POST["firstname"]; ?><br>
Your Last Name is - <?php echo $_POST["lastname"]; ?>
</body>
</html>
Postfix is installed but how do I test it?
To check whether postfix is running or not
sudo postfix status
If it is not running, start it.
sudo postfix start
Then telnet to localhost port 25 to test the email id
ehlo localhost
mail from: root@localhost
rcpt to: your_email_id
data
Subject: My first mail on Postfix
Hi,
Are you there?
regards,
Admin
.
Do not forget the . at the end, which indicates end of line
C++ Array of pointers: delete or delete []?
delete[] monsters;
Is incorrect because monsters
isn't a pointer to a dynamically allocated array, it is an array of pointers. As a class member it will be destroyed automatically when the class instance is destroyed.
Your other implementation is the correct one as the pointers in the array do point to dynamically allocated Monster
objects.
Note that with your current memory allocation strategy you probably want to declare your own copy constructor and copy-assignment operator so that unintentional copying doesn't cause double deletes. (If you you want to prevent copying you could declare them as private and not actually implement them.)
How does one target IE7 and IE8 with valid CSS?
I would recommend looking into conditional comments and making a separate sheet for the IEs you are having problems with.
<!--[if IE 7]>
<link rel="stylesheet" type="text/css" href="ie7.css" />
<![endif]-->
iPad Multitasking support requires these orientations
iPad Multitasking support requires all the orientations but your app does not, so you need to opt out of it, just add the UIRequiresFullScreen
key to your Xcode project’s Info.plist
file and apply the Boolean value YES
.
How do I use namespaces with TypeScript external modules?
Candy Cup Analogy
Version 1: A cup for every candy
Let's say you wrote some code like this:
Mod1.ts
export namespace A {
export class Twix { ... }
}
Mod2.ts
export namespace A {
export class PeanutButterCup { ... }
}
Mod3.ts
export namespace A {
export class KitKat { ... }
}
You've created this setup:
Each module (sheet of paper) gets its own cup named A
. This is useless - you're not actually organizing your candy here, you're just adding an additional step (taking it out of the cup) between you and the treats.
Version 2: One cup in the global scope
If you weren't using modules, you might write code like this (note the lack of export
declarations):
global1.ts
namespace A {
export class Twix { ... }
}
global2.ts
namespace A {
export class PeanutButterCup { ... }
}
global3.ts
namespace A {
export class KitKat { ... }
}
This code creates a merged namespace A
in the global scope:
This setup is useful, but doesn't apply in the case of modules (because modules don't pollute the global scope).
Version 3: Going cupless
Going back to the original example, the cups A
, A
, and A
aren't doing you any favors. Instead, you could write the code as:
Mod1.ts
export class Twix { ... }
Mod2.ts
export class PeanutButterCup { ... }
Mod3.ts
export class KitKat { ... }
to create a picture that looks like this:
Much better!
Now, if you're still thinking about how much you really want to use namespace with your modules, read on...
These Aren't the Concepts You're Looking For
We need to go back to the origins of why namespaces exist in the first place and examine whether those reasons make sense for external modules.
Organization: Namespaces are handy for grouping together logically-related objects and types. For example, in C#, you're going to find all the collection types in System.Collections
. By organizing our types into hierarchical namespaces, we provide a good "discovery" experience for users of those types.
Name Conflicts: Namespaces are important to avoid naming collisions. For example, you might have My.Application.Customer.AddForm
and My.Application.Order.AddForm
-- two types with the same name, but a different namespace. In a language where all identifiers exist in the same root scope and all assemblies load all types, it's critical to have everything be in a namespace.
Do those reasons make sense in external modules?
Organization: External modules are already present in a file system, necessarily. We have to resolve them by path and filename, so there's a logical organization scheme for us to use. We can have a /collections/generic/
folder with a list
module in it.
Name Conflicts: This doesn't apply at all in external modules. Within a module, there's no plausible reason to have two objects with the same name. From the consumption side, the consumer of any given module gets to pick the name that they will use to refer to the module, so accidental naming conflicts are impossible.
Even if you don't believe that those reasons are adequately addressed by how modules work, the "solution" of trying to use namespaces in external modules doesn't even work.
Boxes in Boxes in Boxes
A story:
Your friend Bob calls you up. "I have a great new organization scheme in my house", he says, "come check it out!". Neat, let's go see what Bob has come up with.
You start in the kitchen and open up the pantry. There are 60 different boxes, each labelled "Pantry". You pick a box at random and open it. Inside is a single box labelled "Grains". You open up the "Grains" box and find a single box labelled "Pasta". You open the "Pasta" box and find a single box labelled "Penne". You open this box and find, as you expect, a bag of penne pasta.
Slightly confused, you pick up an adjacent box, also labelled "Pantry". Inside is a single box, again labelled "Grains". You open up the "Grains" box and, again, find a single box labelled "Pasta". You open the "Pasta" box and find a single box, this one is labelled "Rigatoni". You open this box and find... a bag of rigatoni pasta.
"It's great!" says Bob. "Everything is in a namespace!".
"But Bob..." you reply. "Your organization scheme is useless. You have to open up a bunch of boxes to get to anything, and it's not actually any more convenient to find anything than if you had just put everything in one box instead of three. In fact, since your pantry is already sorted shelf-by-shelf, you don't need the boxes at all. Why not just set the pasta on the shelf and pick it up when you need it?"
"You don't understand -- I need to make sure that no one else puts something that doesn't belong in the 'Pantry' namespace. And I've safely organized all my pasta into the Pantry.Grains.Pasta
namespace so I can easily find it"
Bob is a very confused man.
Modules are Their Own Box
You've probably had something similar happen in real life: You order a few things on Amazon, and each item shows up in its own box, with a smaller box inside, with your item wrapped in its own packaging. Even if the interior boxes are similar, the shipments are not usefully "combined".
Going with the box analogy, the key observation is that external modules are their own box. It might be a very complex item with lots of functionality, but any given external module is its own box.
Guidance for External Modules
Now that we've figured out that we don't need to use 'namespaces', how should we organize our modules? Some guiding principles and examples follow.
Export as close to top-level as possible
- If you're only exporting a single class or function, use
export default
:
MyClass.ts
export default class SomeType {
constructor() { ... }
}
MyFunc.ts
function getThing() { return 'thing'; }
export default getThing;
Consumption
import t from './MyClass';
import f from './MyFunc';
var x = new t();
console.log(f());
This is optimal for consumers. They can name your type whatever they want (t
in this case) and don't have to do any extraneous dotting to find your objects.
- If you're exporting multiple objects, put them all at top-level:
MyThings.ts
export class SomeType { ... }
export function someFunc() { ... }
Consumption
import * as m from './MyThings';
var x = new m.SomeType();
var y = m.someFunc();
- If you're exporting a large number of things, only then should you use the
module
/namespace
keyword:
MyLargeModule.ts
export namespace Animals {
export class Dog { ... }
export class Cat { ... }
}
export namespace Plants {
export class Tree { ... }
}
Consumption
import { Animals, Plants} from './MyLargeModule';
var x = new Animals.Dog();
Red Flags
All of the following are red flags for module structuring. Double-check that you're not trying to namespace your external modules if any of these apply to your files:
- A file whose only top-level declaration is
export module Foo { ... }
(remove Foo
and move everything 'up' a level)
- A file that has a single
export class
or export function
that isn't export default
- Multiple files that have the same
export module Foo {
at top-level (don't think that these are going to combine into one Foo
!)
Label axes on Seaborn Barplot
Seaborn's barplot returns an axis-object (not a figure). This means you can do the following:
import pandas as pd
import seaborn as sns
import matplotlib.pyplot as plt
fake = pd.DataFrame({'cat': ['red', 'green', 'blue'], 'val': [1, 2, 3]})
ax = sns.barplot(x = 'val', y = 'cat',
data = fake,
color = 'black')
ax.set(xlabel='common xlabel', ylabel='common ylabel')
plt.show()
How to make a vertical SeekBar in Android?
Try this
import android.content.Context;
import android.graphics.Canvas;
import android.support.annotation.NonNull;
import android.util.AttributeSet;
import android.view.MotionEvent;
import android.widget.SeekBar;
/**
* Implementation of an easy vertical SeekBar, based on the normal SeekBar.
*/
public class VerticalSeekBar extends SeekBar {
/**
* The angle by which the SeekBar view should be rotated.
*/
private static final int ROTATION_ANGLE = -90;
/**
* A change listener registrating start and stop of tracking. Need an own listener because the listener in SeekBar
* is private.
*/
private OnSeekBarChangeListener mOnSeekBarChangeListener;
/**
* Standard constructor to be implemented for all views.
*
* @param context The Context the view is running in, through which it can access the current theme, resources, etc.
* @see android.view.View#View(Context)
*/
public VerticalSeekBar(final Context context) {
super(context);
}
/**
* Standard constructor to be implemented for all views.
*
* @param context The Context the view is running in, through which it can access the current theme, resources, etc.
* @param attrs The attributes of the XML tag that is inflating the view.
* @see android.view.View#View(Context, AttributeSet)
*/
public VerticalSeekBar(final Context context, final AttributeSet attrs) {
super(context, attrs);
}
/**
* Standard constructor to be implemented for all views.
*
* @param context The Context the view is running in, through which it can access the current theme, resources, etc.
* @param attrs The attributes of the XML tag that is inflating the view.
* @param defStyle An attribute in the current theme that contains a reference to a style resource that supplies default
* values for the view. Can be 0 to not look for defaults.
* @see android.view.View#View(Context, AttributeSet, int)
*/
public VerticalSeekBar(final Context context, final AttributeSet attrs, final int defStyle) {
super(context, attrs, defStyle);
}
/*
* (non-Javadoc) ${see_to_overridden}
*/
@Override
protected final void onSizeChanged(final int width, final int height, final int oldWidth, final int oldHeight) {
super.onSizeChanged(height, width, oldHeight, oldWidth);
}
/*
* (non-Javadoc) ${see_to_overridden}
*/
@Override
protected final synchronized void onMeasure(final int widthMeasureSpec, final int heightMeasureSpec) {
super.onMeasure(heightMeasureSpec, widthMeasureSpec);
setMeasuredDimension(getMeasuredHeight(), getMeasuredWidth());
}
/*
* (non-Javadoc) ${see_to_overridden}
*/
@Override
protected final void onDraw(@NonNull final Canvas c) {
c.rotate(ROTATION_ANGLE);
c.translate(-getHeight(), 0);
super.onDraw(c);
}
/*
* (non-Javadoc) ${see_to_overridden}
*/
@Override
public final void setOnSeekBarChangeListener(final OnSeekBarChangeListener listener) {
// Do not use super for the listener, as this would not set the fromUser flag properly
mOnSeekBarChangeListener = listener;
}
/*
* (non-Javadoc) ${see_to_overridden}
*/
@Override
public final boolean onTouchEvent(@NonNull final MotionEvent event) {
if (!isEnabled()) {
return false;
}
switch (event.getAction()) {
case MotionEvent.ACTION_DOWN:
setProgressInternally(getMax() - (int) (getMax() * event.getY() / getHeight()), true);
if (mOnSeekBarChangeListener != null) {
mOnSeekBarChangeListener.onStartTrackingTouch(this);
}
break;
case MotionEvent.ACTION_MOVE:
setProgressInternally(getMax() - (int) (getMax() * event.getY() / getHeight()), true);
break;
case MotionEvent.ACTION_UP:
setProgressInternally(getMax() - (int) (getMax() * event.getY() / getHeight()), true);
if (mOnSeekBarChangeListener != null) {
mOnSeekBarChangeListener.onStopTrackingTouch(this);
}
break;
case MotionEvent.ACTION_CANCEL:
if (mOnSeekBarChangeListener != null) {
mOnSeekBarChangeListener.onStopTrackingTouch(this);
}
break;
default:
break;
}
return true;
}
/**
* Set the progress by the user. (Unfortunately, Seekbar.setProgressInternally(int, boolean) is not accessible.)
*
* @param progress the progress.
* @param fromUser flag indicating if the change was done by the user.
*/
public final void setProgressInternally(final int progress, final boolean fromUser) {
if (progress != getProgress()) {
super.setProgress(progress);
if (mOnSeekBarChangeListener != null) {
mOnSeekBarChangeListener.onProgressChanged(this, progress, fromUser);
}
}
onSizeChanged(getWidth(), getHeight(), 0, 0);
}
/*
* (non-Javadoc) ${see_to_overridden}
*/
@Override
public final void setProgress(final int progress) {
setProgressInternally(progress, false);
}
}
check if a std::vector contains a certain object?
Checking if v
contains the element x
:
#include <algorithm>
if(std::find(v.begin(), v.end(), x) != v.end()) {
/* v contains x */
} else {
/* v does not contain x */
}
Checking if v
contains elements (is non-empty):
if(!v.empty()){
/* v is non-empty */
} else {
/* v is empty */
}
Parsing a YAML file in Python, and accessing the data?
Since PyYAML's yaml.load()
function parses YAML documents to native Python data structures, you can just access items by key or index. Using the example from the question you linked:
import yaml
with open('tree.yaml', 'r') as f:
doc = yaml.load(f)
To access branch1 text
you would use:
txt = doc["treeroot"]["branch1"]
print txt
"branch1 text"
because, in your YAML document, the value of the branch1
key is under the treeroot
key.
how to change language for DataTable
You have to either create a language file and then set it using :
"oLanguage": {
"sUrl": "media/language/your_file.txt"
}
Im not sure what server language you are using but something like this would work in PHP :
"oLanguage": {
"sUrl": "media/language/custom_lang_<?php echo $language ?>.txt"
}
Where language
matches the file name for a specific language.
or change individual settings :
"oLanguage": {
"sLengthMenu": "Display _MENU_ records per page",
"sZeroRecords": "Nothing found - sorry",
"sInfo": "Showing _START_ to _END_ of _TOTAL_ records",
"sInfoEmpty": "Showing 0 to 0 of 0 records",
"sInfoFiltered": "(filtered from _MAX_ total records)"
}
For more details read this : http://datatables.net/plug-ins/i18n
printing out a 2-D array in Matrix format
In java8 fashion:
import java.util.Arrays;
public class MatrixPrinter {
public static void main(String[] args) {
final int[][] matrix = new int[4][4];
printMatrix(matrix);
}
public static void printMatrix(int[][] matrix) {
Arrays.stream(matrix)
.forEach(
(row) -> {
System.out.print("[");
Arrays.stream(row)
.forEach((el) -> System.out.print(" " + el + " "));
System.out.println("]");
}
);
}
}
this produces
[ 0 0 0 0 ]
[ 0 0 0 0 ]
[ 0 0 0 0 ]
[ 0 0 0 0 ]
but since we are here why not make the row layout customisable?
All we need is to pass a lamba to the matrixPrinter method:
import java.util.Arrays;
import java.util.function.Consumer;
public class MatrixPrinter {
public static void main(String[] args) {
final int[][] matrix = new int[3][3];
Consumer<int[]> noDelimiter = (row) -> {
Arrays.stream(row).forEach((el) -> System.out.print(" " + el + " "));
System.out.println();
};
Consumer<int[]> pipeDelimiter = (row) -> {
Arrays.stream(row).forEach((el) -> System.out.print("| " + el + " "));
System.out.println("|");
};
Consumer<int[]> likeAList = (row) -> {
System.out.print("[");
Arrays.stream(row)
.forEach((el) -> System.out.print(" " + el + " "));
System.out.println("]");
};
printMatrix(matrix, noDelimiter);
System.out.println();
printMatrix(matrix, pipeDelimiter);
System.out.println();
printMatrix(matrix, likeAList);
}
public static void printMatrix(int[][] matrix, Consumer<int[]> rowPrinter) {
Arrays.stream(matrix)
.forEach((row) -> rowPrinter.accept(row));
}
}
this is the result :
0 0 0
0 0 0
0 0 0
| 0 | 0 | 0 |
| 0 | 0 | 0 |
| 0 | 0 | 0 |
[ 0 0 0 ]
[ 0 0 0 ]
[ 0 0 0 ]
Functional programming vs Object Oriented programming
Object Oriented Programming offers:
- Encapsulation, to
- control mutation of internal state
- limit coupling to internal representation
- Subtyping, allowing:
- substitution of compatible types (polymorphism)
- a crude means of sharing implementation between classes (implementation inheritance)
Functional Programming, in Haskell or even in Scala, can allow substitution through more general mechanism of type classes. Mutable internal state is either discouraged or forbidden. Encapsulation of internal representation can also be achieved. See Haskell vs OOP for a good comparison.
Norman's assertion that "Adding a new kind of thing to a functional program may require editing many function definitions to add a new case." depends on how well the functional code has employed type classes. If Pattern Matching on a particular Abstract Data Type is spread throughout a codebase, you will indeed suffer from this problem, but it is perhaps a poor design to start with.
EDITED Removed reference to implicit conversions when discussing type classes. In Scala, type classes are encoded with implicit parameters, not conversions, although implicit conversions are another means to acheiving substitution of compatible types.
How to get domain URL and application name?
If you are being passed a url as a String and want to extract the context root of that application, you can use this regex to extract it. It will work for full urls or relative urls that begin with the context root.
url.replaceAll("^(.*\\/\\/)?.*?\\/(.+?)\\/.*|\\/(.+)$", "$2$3")
Enable/Disable Anchor Tags using AngularJS
Modifying @Nitin's answer to work with dynamic disabling:
angular.module('myApp').directive('a', function() {
return {
restrict: 'E',
link: function(scope, elem, attrs) {
elem.on('click', function(e) {
if (attrs.disabled) {
e.preventDefault(); // prevent link click
}
});
}
};
});
This checks the existence of disabled attribute and its value upon every click.
How to give a user only select permission on a database
For the GUI minded people, you can:
- Right click the Database in Management Studio.
- Choose Properties
- Select Permissions
- If your user does not show up in the list, choose Search and type their name
- Select the user in the Users or Roles list
- In the lower window frame, Check the Select permission under the Grant column
Java Spring Boot: How to map my app root (“/”) to index.html?
You can add a RedirectViewController like:
@Configuration
public class WebConfiguration implements WebMvcConfigurer {
@Override
public void addViewControllers(ViewControllerRegistry registry) {
registry.addRedirectViewController("/", "/index.html");
}
}
Upload file to FTP using C#
The existing answers are valid, but why re-invent the wheel and bother with lower level WebRequest
types while WebClient
already implements FTP uploading neatly:
using (var client = new WebClient())
{
client.Credentials = new NetworkCredential(ftpUsername, ftpPassword);
client.UploadFile("ftp://host/path.zip", WebRequestMethods.Ftp.UploadFile, localFile);
}
Get a list of distinct values in List
public class KeyNote
{
public long KeyNoteId { get; set; }
public long CourseId { get; set; }
public string CourseName { get; set; }
public string Note { get; set; }
public DateTime CreatedDate { get; set; }
}
public List<KeyNote> KeyNotes { get; set; }
public List<RefCourse> GetCourses { get; set; }
List<RefCourse> courses = KeyNotes.Select(x => new RefCourse { CourseId = x.CourseId, Name = x.CourseName }).Distinct().ToList();
By using the above logic, we can get the unique Course
s.
Makefile If-Then Else and Loops
Here's an example if:
ifeq ($(strip $(OS)),Linux)
PYTHON = /usr/bin/python
FIND = /usr/bin/find
endif
Note that this comes with a word of warning that different versions of Make have slightly different syntax, none of which seems to be documented very well.
How to reverse a singly linked list using only two pointers?
#include <stddef.h>
typedef struct Node {
struct Node *next;
int data;
} Node;
Node * reverse(Node *cur) {
Node *prev = NULL;
while (cur) {
Node *temp = cur;
cur = cur->next; // advance cur
temp->next = prev;
prev = temp; // advance prev
}
return prev;
}
Git - Ignore files during merge
Example:
- You have two branches:
master
, develop
- You created file in
develop
branch and want to ignore it while merging
Code:
git config --global merge.ours.driver true
git checkout master
echo "path/file_to_ignore merge=ours" >> .gitattributes
git merge develop
You can also ignore files with same extension
for example all files with .txt
extension:
echo "*.txt merge=ours" >> .gitattributes
Showing all errors and warnings
Display errors could be turned off in the php.ini
or your Apache configuration file.
You can turn it on in the script:
error_reporting(E_ALL);
ini_set('display_errors', '1');
You should see the same messages in the PHP error log.
Append an array to another array in JavaScript
If you want to modify the original array instead of returning a new array, use .push()
...
array1.push.apply(array1, array2);
array1.push.apply(array1, array3);
I used .apply
to push the individual members of arrays 2
and 3
at once.
or...
array1.push.apply(array1, array2.concat(array3));
To deal with large arrays, you can do this in batches.
for (var n = 0, to_add = array2.concat(array3); n < to_add.length; n+=300) {
array1.push.apply(array1, to_add.slice(n, n+300));
}
If you do this a lot, create a method or function to handle it.
var push_apply = Function.apply.bind([].push);
var slice_call = Function.call.bind([].slice);
Object.defineProperty(Array.prototype, "pushArrayMembers", {
value: function() {
for (var i = 0; i < arguments.length; i++) {
var to_add = arguments[i];
for (var n = 0; n < to_add.length; n+=300) {
push_apply(this, slice_call(to_add, n, n+300));
}
}
}
});
and use it like this:
array1.pushArrayMembers(array2, array3);
_x000D_
_x000D_
var push_apply = Function.apply.bind([].push);_x000D_
var slice_call = Function.call.bind([].slice);_x000D_
_x000D_
Object.defineProperty(Array.prototype, "pushArrayMembers", {_x000D_
value: function() {_x000D_
for (var i = 0; i < arguments.length; i++) {_x000D_
var to_add = arguments[i];_x000D_
for (var n = 0; n < to_add.length; n+=300) {_x000D_
push_apply(this, slice_call(to_add, n, n+300));_x000D_
}_x000D_
}_x000D_
}_x000D_
});_x000D_
_x000D_
var array1 = ['a','b','c'];_x000D_
var array2 = ['d','e','f'];_x000D_
var array3 = ['g','h','i'];_x000D_
_x000D_
array1.pushArrayMembers(array2, array3);_x000D_
_x000D_
document.body.textContent = JSON.stringify(array1, null, 4);
_x000D_
_x000D_
_x000D_
How to grant permission to users for a directory using command line in Windows?
excellent point Calin Darie
I had a lot of scripts to use cacls I move them to icacls
how ever I could not find a script to change the root mount volumes example: d:\datafolder. I finally crated the script below, which mounts the volume as a temporary drive then applies sec. then unmounts it. It is the only way I found that you can update the root mount security.
1 gets the folder mount GUID to a temp file then reads the GUID to mount the volume as a temp drive X: applies sec and logs the changes then unmounts the Volume only from the X: drive so the mounted folder is not altered or interrupted other then the applied sec.
here is sample of my script:
**mountvol "d:\%1" /L >tempDrive.temp && FOR /f "tokens=*" %%I IN (tempDrive.temp) DO mountvol X: %%I
D:\tools\security\icacls.exe %~2 /grant domain\group:(OI)(CI)F /T /C >>%~1LUNsec-%TDWEEK%-%TMONTH%-%TDAY%-%TYEAR%-%THOUR%-%TMINUTE%-%TAM%.txt
if exist x:\*.* mountvol X: /d**
How to install Selenium WebDriver on Mac OS
Install
If you use homebrew (which I recommend), you can install selenium using:
brew install selenium-server-standalone
Running
updated -port port_number
To run selenium, do: selenium-server -port 4444
For more options: selenium-server -help
Which port we can use to run IIS other than 80?
I'm going to make a few assumptions and come at the problem from a different angle... in that because you have skype installed and running on the same machine, that it is not a production machine and instead used for testing / development?
If so, you may wish to look at alternatives to IIS completely to alleviate your issue. If you use IISExpress or the web server built into recent versions of Visual Studio, they will automatically pick a port for you.
Of course this does mean that it's not particularly useful for giving other people access, but is fine for local development for personal use.
I think the other answers probably offer a better alternative in most situations, but this may offer a different insight.
Here is an intro to IIS Express: http://learn.iis.net/page.aspx/860/iis-express/
org.hibernate.NonUniqueResultException: query did not return a unique result: 2?
Generally This exception is thrown from Oracle when query result (which is stored in an Object in your case), can not be cast to the desired object.
for example when result is a
List<T>
and you're putting the result into a single T object.
In case of casting to long error, besides it is recommended to use wrapper classes so that all of your columns act the same, I guess a problem in transaction or query itself would cause this issue.
WRONGTYPE Operation against a key holding the wrong kind of value php
I faced this issue when trying to set something to redis. The problem was that I previously used "set" method to set data with a certain key, like
$redis->set('persons', $persons)
Later I decided to change to "hSet" method, and I tried it this way
foreach($persons as $person){
$redis->hSet('persons', $person->id, $person);
}
Then I got the aforementioned error. So, what I had to do is to go to redis-cli and manually delete "persons" entry with
del persons
It simply couldn't write different data structure under existing key, so I had to delete the entry and hSet then.
Compare two objects in Java with possible null values
OK, so what does "best possible solution" mean?
If you mean most readable, then all the possible solutions are pretty much equivalent for an experienced Java programmer. But IMO the most readable is this
public boolean compareStringsOrNulls(String str1, String str2) {
// Implement it how you like
}
In other words, hide the implementation inside a simple method that (ideally) can be inlined.
(You could also "out-source" to a 3rd party utility library ... if you already use it in your codebase.)
If you mean most performant, then:
- the most performant solution depends on the platform and the context,
- one of the "context" issues is the relative (dynamic) frequency of occurrence of
null
arguments,
- it probably doesn't matter which version is faster ... because the difference is probably too small to make a difference to the overall application performance, and
- if it does matter, the only way to figure out which is fastest ON YOUR PLATFORM is to try both versions and measure the difference.
How to set Linux environment variables with Ansible
There are multiple ways to do this and from your question it's nor clear what you need.
1. If you need environment variable to be defined PER TASK ONLY, you do this:
- hosts: dev
tasks:
- name: Echo my_env_var
shell: "echo $MY_ENV_VARIABLE"
environment:
MY_ENV_VARIABLE: whatever_value
- name: Echo my_env_var again
shell: "echo $MY_ENV_VARIABLE"
Note that MY_ENV_VARIABLE
is available ONLY for the first task, environment
does not set it permanently on your system.
TASK: [Echo my_env_var] *******************************************************
changed: [192.168.111.222] => {"changed": true, "cmd": "echo $MY_ENV_VARIABLE", ... "stdout": "whatever_value"}
TASK: [Echo my_env_var again] *************************************************
changed: [192.168.111.222] => {"changed": true, "cmd": "echo $MY_ENV_VARIABLE", ... "stdout": ""}
Hopefully soon using environment
will also be possible on play level, not only task level as above.
There's currently a pull request open for this feature on Ansible's GitHub: https://github.com/ansible/ansible/pull/8651
UPDATE: It's now merged as of Jan 2, 2015.
2. If you want permanent environment variable + system wide / only for certain user
You should look into how you do it in your Linux distribution / shell, there are multiple places for that. For example in Ubuntu you define that in files like for example:
~/.profile
/etc/environment
/etc/profile.d
directory
- ...
You will find Ubuntu docs about it here: https://help.ubuntu.com/community/EnvironmentVariables
After all for setting environment variable in ex. Ubuntu you can just use lineinfile
module from Ansible and add desired line to certain file. Consult your OS docs to know where to add it to make it permanent.
How do I get an Excel range using row and column numbers in VSTO / C#?
If you want like Cells(Rows.Count, 1).End(xlUp).Row
, you can do it.
just use the following code:
using Excel = Microsoft.Office.Interop.Excel;
string xlBk = @"D:\Test.xlsx";
Excel.Application xlApp;
Excel.Workbook xlWb;
Excel.Worksheet xlWs;
Excel.Range rng;
int iLast;
xlApp = new Excel.Application();
xlWb = xlApp.Workbooks.Open(xlBk, 0, true, 5, "", "", true,
Microsoft.Office.Interop.Excel.XlPlatform.xlWindows, "\t", false, false, 0, true, 1, 0);
xlWs = (Excel.Worksheet)xlWb.Worksheets.get_Item(1);
iLast = xlWs.Rows.Count;
rng = (Excel.Range)xlWs.Cells[iLast, 1];
iLast = rng.get_End(Excel.XlDirection.xlUp).Row;
cURL POST command line on WINDOWS RESTful service
I ran into the same issue on my win7 x64 laptop and was able to get it working using the curl release that is labeled Win64 - Generic w SSL by using the very similar command line format:
C:\Projects\curl-7.23.1-win64-ssl-sspi>curl -H "Content-Type: application/json" -X POST http://localhost/someapi -d "{\"Name\":\"Test Value\"}"
Which only differs from your 2nd escape version by using double-quotes around the escaped ones and the header parameter value. Definitely prefer the linux shell syntax more.
What is ViewModel in MVC?
View model is same as your datamodel but you can add 2 or more data model classes in it. According to that you have to change your controller to take 2 models at once
Is it better to use C void arguments "void foo(void)" or not "void foo()"?
Besides syntactical differences, many people also prefer using void function(void)
for pracitical reasons:
If you're using the search function and want to find the implementation of the function, you can search for function(void)
, and it will return the prototype as well as the implementation.
If you omit the void
, you have to search for function()
and will therefore also find all function calls, making it more difficult to find the actual implementation.
How do I get multiple subplots in matplotlib?
Iterating through all subplots sequentially:
fig, axes = plt.subplots(nrows, ncols)
for ax in axes.flatten():
ax.plot(x,y)
Accessing a specific index:
for row in range(nrows):
for col in range(ncols):
axes[row,col].plot(x[row], y[col])
Watching variables in SSIS during debug
I know this is very old and possibly talking about an older version of Visual studio and so this might not have been an option before but anyway, my way would be when at a breakpoint use the locals window to see all current variable values ( Debug >> Windows >> Locals )
SQL Server: Filter output of sp_who2
Extension of the first and best answer... I have created a stored procedure on the master database that you can then pass parameters to .. such as the name of the database:
USE master
GO
CREATE PROCEDURE sp_who_db
(
@sDBName varchar(200) = null,
@sStatus varchar(200) = null,
@sCommand varchar(200) = null,
@nCPUTime int = null
)
AS
DECLARE @Table TABLE
(
SPID INT,
Status VARCHAR(MAX),
LOGIN VARCHAR(MAX),
HostName VARCHAR(MAX),
BlkBy VARCHAR(MAX),
DBName VARCHAR(MAX),
Command VARCHAR(MAX),
CPUTime INT,
DiskIO INT,
LastBatch VARCHAR(MAX),
ProgramName VARCHAR(MAX),
SPID_1 INT,
REQUESTID INT
)
INSERT INTO @Table EXEC sp_who2
SELECT *
FROM @Table
WHERE (@sDBName IS NULL OR DBName = @sDBName)
AND (@sStatus IS NULL OR Status = @sStatus)
AND (@sCommand IS NULL OR Command = @sCommand)
AND (@nCPUTime IS NULL OR CPUTime > @nCPUTime)
GO
I might extend it to add an order by parameter or even a kill paramatmer so it kills all connections to a particular data
How can I compare two dates in PHP?
I would'nt do this with PHP.
A database should know, what day is today.( use MySQL->NOW() for example ), so it will be very easy to compare within the Query and return the result, without any problems depending on the used Date-Types
SELECT IF(expireDate < NOW(),TRUE,FALSE) as isExpired FROM tableName
Using $state methods with $stateChangeStart toState and fromState in Angular ui-router
Suggestion 1
When you add an object to $stateProvider.state
that object is then passed with the state. So you can add additional properties which you can read later on when needed.
Example route configuration
$stateProvider
.state('public', {
abstract: true,
module: 'public'
})
.state('public.login', {
url: '/login',
module: 'public'
})
.state('tool', {
abstract: true,
module: 'private'
})
.state('tool.suggestions', {
url: '/suggestions',
module: 'private'
});
The $stateChangeStart
event gives you acces to the toState
and fromState
objects. These state objects will contain the configuration properties.
Example check for the custom module property
$rootScope.$on('$stateChangeStart', function(e, toState, toParams, fromState, fromParams) {
if (toState.module === 'private' && !$cookies.Session) {
// If logged out and transitioning to a logged in page:
e.preventDefault();
$state.go('public.login');
} else if (toState.module === 'public' && $cookies.Session) {
// If logged in and transitioning to a logged out page:
e.preventDefault();
$state.go('tool.suggestions');
};
});
I didn't change the logic of the cookies because I think that is out of scope for your question.
Suggestion 2
You can create a Helper to get you this to work more modular.
Value publicStates
myApp.value('publicStates', function(){
return {
module: 'public',
routes: [{
name: 'login',
config: {
url: '/login'
}
}]
};
});
Value privateStates
myApp.value('privateStates', function(){
return {
module: 'private',
routes: [{
name: 'suggestions',
config: {
url: '/suggestions'
}
}]
};
});
The Helper
myApp.provider('stateshelperConfig', function () {
this.config = {
// These are the properties we need to set
// $stateProvider: undefined
process: function (stateConfigs){
var module = stateConfigs.module;
$stateProvider = this.$stateProvider;
$stateProvider.state(module, {
abstract: true,
module: module
});
angular.forEach(stateConfigs, function (route){
route.config.module = module;
$stateProvider.state(module + route.name, route.config);
});
}
};
this.$get = function () {
return {
config: this.config
};
};
});
Now you can use the helper to add the state configuration to your state configuration.
myApp.config(['$stateProvider', '$urlRouterProvider',
'stateshelperConfigProvider', 'publicStates', 'privateStates',
function ($stateProvider, $urlRouterProvider, helper, publicStates, privateStates) {
helper.config.$stateProvider = $stateProvider;
helper.process(publicStates);
helper.process(privateStates);
}]);
This way you can abstract the repeated code, and come up with a more modular solution.
Note: the code above isn't tested
foreach with index
This is your collection
var values = new[] {6, 2, 8, 45, 9, 3, 0};
Make a range of indexes for this collection
var indexes = Enumerable.Range(0, values.Length).ToList();
Use the range to iterate with index
indexes.ForEach(i => values[i] += i);
indexes.ForEach(i => Console.Write("[{0}] = {1}", i, values[i]));
Returning a boolean from a Bash function
For code readability reasons I believe returning true/false should:
- be on one line
- be one command
- be easy to remember
- mention the keyword
return
followed by another keyword (true
or false
)
My solution is return $(true)
or return $(false)
as shown:
is_directory()
{
if [ -d "${1}" ]; then
return $(true)
else
return $(false)
fi
}
Java SSLHandshakeException "no cipher suites in common"
Server
import java.net.*;
import java.io.*;
import java.util.*;
import javax.net.ssl.*;
import javax.net.*;
class Test{
public static void main(String[] args){
try{
SSLContext context = SSLContext.getInstance("TLSv1.2");
context.init(null,null,null);
SSLServerSocketFactory serverSocketFactory = context.getServerSocketFactory();
SSLServerSocket server = (SSLServerSocket)serverSocketFactory.createServerSocket(1024);
server.setEnabledCipherSuites(server.getSupportedCipherSuites());
SSLSocket socket = (SSLSocket)server.accept();
DataInputStream in = new DataInputStream(socket.getInputStream());
DataOutputStream out = new DataOutputStream(socket.getOutputStream());
System.out.println(in.readInt());
}catch(Exception e){e.printStackTrace();}
}
}
Client
import java.net.*;
import java.io.*;
import java.util.*;
import javax.net.ssl.*;
import javax.net.*;
class Test2{
public static void main(String[] args){
try{
SSLContext context = SSLContext.getInstance("TLSv1.2");
context.init(null,null,null);
SSLSocketFactory socketFactory = context.getSocketFactory();
SSLSocket socket = (SSLSocket)socketFactory.createSocket("localhost", 1024);
socket.setEnabledCipherSuites(socket.getSupportedCipherSuites());
DataInputStream in = new DataInputStream(socket.getInputStream());
DataOutputStream out = new DataOutputStream(socket.getOutputStream());
out.writeInt(1337);
}catch(Exception e){e.printStackTrace();}
}
}
server.setEnabledCipherSuites(server.getSupportedCipherSuites());
socket.setEnabledCipherSuites(socket.getSupportedCipherSuites());
Call Jquery function
To call the function on click of some html element (control).
$('#controlID').click(myFunction);
You will need to ensure you bind the event when your html element is ready on which you binding the event. You can put the code in document.ready
$(document).ready(function(){
$('#controlID').click(myFunction);
});
You can use anonymous function to bind the event to the html element.
$(document).ready(function(){
$('#controlID').click(function(){
$.messager.show({
title:'My Title',
msg:'The message content',
showType:'fade',
style:{
right:'',
bottom:''
}
});
});
});
If you want to bind click with many elements you can use class selector
$('.someclass').click(myFunction);
Edit based on comments by OP, If you want to call function under some condition
You can use if for conditional execution, for example,
if(a == 3)
myFunction();
RE error: illegal byte sequence on Mac OS X
Does anyone know how to get sed to print the position of the illegal byte sequence? Or does anyone know what the illegal byte sequence is?
$ uname -a
Darwin Adams-iMac 18.7.0 Darwin Kernel Version 18.7.0: Tue Aug 20 16:57:14 PDT 2019; root:xnu-4903.271.2~2/RELEASE_X86_64 x86_64
I got part of the way to answering the above just by using tr.
I have a .csv file that is a credit card statement and I am trying to import it into Gnucash. I am based in Switzerland so I have to deal with words like Zürich. Suspecting Gnucash does not like " " in numeric fields, I decide to simply replace all
; ;
with
;;
Here goes:
$ head -3 Auswertungen.csv | tail -1 | sed -e 's/; ;/;;/g'
sed: RE error: illegal byte sequence
I used od to shed some light: Note the 374 halfway down this od -c output
$ head -3 Auswertungen.csv | tail -1 | od -c
0000000 1 6 8 7 9 6 1 9 7 1 2 2 ; 5
0000020 4 6 8 8 7 X X X X X X 2 6
0000040 6 0 ; M Y N A M E I S X ; 1
0000060 4 . 0 2 . 2 0 1 9 ; 9 5 5 2 -
0000100 M i t a r b e i t e r r e s t
0000120 Z 374 r i c h
0000140 C H E ; R e s t a u r a n t s ,
0000160 B a r s ; 6 . 2 0 ; C H F ;
0000200 ; C H F ; 6 . 2 0 ; ; 1 5 . 0
0000220 2 . 2 0 1 9 \n
0000227
Then I thought I might try to persuade tr to substitute 374 for whatever the correct byte code is. So first I tried something simple, which didn't work, but had the side effect of showing me where the troublesome byte was:
$ head -3 Auswertungen.csv | tail -1 | tr . . ; echo
tr: Illegal byte sequence
1687 9619 7122;5468 87XX XXXX 2660;MY NAME ISX;14.02.2019;9552 - Mitarbeiterrest Z
You can see tr bails at the 374 character.
Using perl seems to avoid this problem
$ head -3 Auswertungen.csv | tail -1 | perl -pne 's/; ;/;;/g'
1687 9619 7122;5468 87XX XXXX 2660;ADAM NEALIS;14.02.2019;9552 - Mitarbeiterrest Z?rich CHE;Restaurants, Bars;6.20;CHF;;CHF;6.20;;15.02.2019
Build and Install unsigned apk on device without the development server?
Generate debug APK without dev-server
If you really want to generate a debug APK (for testing purpose) that can run without the development server, Congrats! here I am to help you. :)
Everyone is saying that we need to run two commands react-native bundle ...
and then gradlew assembleDebug
but the generated APK still doesnot work without development server. After many research & try I figured out that we need to change in the gradle file (as in step-2). Just follow these steps:
- In your react native project go to
/android/app/src/main
create a folder assets
- edit
android > app > build.gradle
project.ext.react = [
...
bundleInDebug: true, // add this line
]
- run this command at the root directory of your react native project
react-native bundle --platform android --dev false --entry-file index.js --bundle-output android/app/src/main/assets/index.android.bundle --assets-dest android/app/src/main/res
- Now, go into the android folder:
cd android
- And, run this command:
gradlew assembleDebug
(if build failed, try building assembleDebug from android studio)
This will create app-debug.apk
file in android/app/build/outputs/apk/debug
directory, which you can install & run without dev-server.
Why .NET String is immutable?
Why are string types immutable in C#
String is a reference type, so it is never copied, but passed by reference.
Compare this to the C++ std::string
object (which is not immutable), which
is passed by value. This means that if
you want to use a String as a key in a
Hashtable, you're fine in C++, because
C++ will copy the string to store the
key in the hashtable (actually
std::hash_map, but still) for later
comparison. So even if you later
modify the std::string instance,
you're fine. But in .Net, when you use
a String in a Hashtable, it will store
a reference to that instance. Now
assume for a moment that strings
aren't immutable, and see what
happens:
1. Somebody inserts a value x with key "hello" into a Hashtable.
2. The Hashtable computes the hash value for the String, and places a
reference to the string and the value
x in the appropriate bucket.
3. The user modifies the String instance to be "bye".
4. Now somebody wants the value in the hashtable associated with "hello". It
ends up looking in the correct bucket,
but when comparing the strings it says
"bye"!="hello", so no value is
returned.
5. Maybe somebody wants the value "bye"? "bye" probably has a different
hash, so the hashtable would look in a
different bucket. No "bye" keys in
that bucket, so our entry still isn't
found.
Making strings immutable means that
step 3 is impossible. If somebody
modifies the string he's creating a
new string object, leaving the old one
alone. Which means the key in the
hashtable is still "hello", and thus
still correct.
So, probably among other things,
immutable strings are a way to enable
strings that are passed by reference
to be used as keys in a hashtable or
similar dictionary object.
How do I crop an image in Java?
The solution I found most useful for cropping a buffered image uses the getSubImage(x,y,w,h);
My cropping routine ended up looking like this:
private BufferedImage cropImage(BufferedImage src, Rectangle rect) {
BufferedImage dest = src.getSubimage(0, 0, rect.width, rect.height);
return dest;
}
Apply CSS styles to an element depending on its child elements
As far as I'm aware, styling a parent element based on the child element is not an available feature of CSS. You'll likely need scripting for this.
It'd be wonderful if you could do something like div[div.a]
or div:containing[div.a]
as you said, but this isn't possible.
You may want to consider looking at jQuery. Its selectors work very well with 'containing' types. You can select the div, based on its child contents and then apply a CSS class to the parent all in one line.
If you use jQuery, something along the lines of this would may work (untested but the theory is there):
$('div:has(div.a)').css('border', '1px solid red');
or
$('div:has(div.a)').addClass('redBorder');
combined with a CSS class:
.redBorder
{
border: 1px solid red;
}
Here's the documentation for the jQuery "has" selector.
"[notice] child pid XXXX exit signal Segmentation fault (11)" in apache error.log
A segementation fault is an internal error in php (or, less likely, apache). Oftentimes, the segmentation fault is caused by one of the newer and lesser-tested php modules such as imagemagick or subversion.
Try disabling all non-essential modules (in php.ini
), and then re-enabling them one-by-one until the error occurs. You may also want to update php and apache.
If that doesn't help, you should report a php bug.
.rar, .zip files MIME Type
As extension might contain more or less that three characters the following will test for an extension regardless of the length of it.
Try this:
$allowedExtensions = array( 'mkv', 'mp3', 'flac' );
$temp = explode(".", $_FILES[$file]["name"]);
$extension = strtolower(end($temp));
if( in_array( $extension, $allowedExtensions ) ) { ///
to check for all characters after the last '.'
Access blocked by CORS policy: Response to preflight request doesn't pass access control check
Since the originating port 4200 is different than 8080,So before angular sends a create (PUT) request,it will send an OPTIONS request to the server to check what all methods and what all access-controls are in place.
Server has to respond to that OPTIONS request with list of allowed methods and allowed origins.
Since you are using spring boot, the simple solution is to add ".allowedOrigins("http://localhost:4200");"
In your spring config,class
@Configuration
@EnableWebMvc
public class SpringConfig implements WebMvcConfigurer {
@Override
public void addCorsMappings(CorsRegistry registry) {
registry.addMapping("/**").allowedOrigins("http://localhost:4200");
}
}
However a better approach will be to write a Filter(interceptor) which adds the necessary headers to each response.
Remove border from buttons
The usual trick is to make the image itself part of a link instead of a button. Then, you bind the "click" event with a custom handler.
Frameworks like Jquery-UI or Bootstrap does this out of the box. Using one of them may ease a lot the whole application conception by the way.
Redirecting to a new page after successful login
Javascript redirection generated with php code:
if($match > 0){
$msg = 'Login Complete! Thanks';
echo "<script> window.location.assign('index.php'); </script>";
}
else{
$msg = 'Login Failed!<br /> Please make sure that you enter the correct details and that you have activated your account.';
}
Php redirection only:
<?php
header("Location: index.php");
exit;
?>
Jenkins "Console Output" log location in filesystem
This is designed for use when you have a shell script build step. Use only the first two lines to get the file name.
You can get the console log file (using bash magic) for the current build from a shell script this way and check it for some error string, failing the job if found:
logFilename=${JENKINS_HOME}/${JOB_URL:${#JENKINS_URL}}
logFilename=${logFilename//job\//jobs\/}builds/${BUILD_NUMBER}/log
grep "**Failure**" ${logFilename} ; exitCode=$?
[[ $exitCode -ne 1 ]] && exit 1
You have to build the file name by taking the JOB_URL, stripping off the leading host name part, adding in the path to JENKINS_HOME, replacing "/job/" to "/jobs/" to handle all nested folders, adding the current build number and the file name.
The grep returns 0 if the string is found and 2 if there is a file error. So a 1 means it found the error indication string. That makes the build fail.
Eclipse Problems View not showing Errors anymore
Right-click your project and go to Properties > Java Build Path > Source.
Make sure your source directory (for example MyProject/src) is listed as a Source folder. Otherwise you won't get any red markers.
back button callback in navigationController in iOS
If you can't use "viewWillDisappear" or similar method, try to subclass UINavigationController. This is the header class:
#import <Foundation/Foundation.h>
@class MyViewController;
@interface CCNavigationController : UINavigationController
@property (nonatomic, strong) MyViewController *viewController;
@end
Implementation class:
#import "CCNavigationController.h"
#import "MyViewController.h"
@implementation CCNavigationController {
}
- (UIViewController *)popViewControllerAnimated:(BOOL)animated {
@"This is the moment for you to do whatever you want"
[self.viewController doCustomMethod];
return [super popViewControllerAnimated:animated];
}
@end
In the other hand, you need to link this viewController to your custom NavigationController, so, in your viewDidLoad method for your regular viewController do this:
@implementation MyViewController {
- (void)viewDidLoad
{
[super viewDidLoad];
((CCNavigationController*)self.navigationController).viewController = self;
}
}
What's the difference between <mvc:annotation-driven /> and <context:annotation-config /> in servlet?
<context:annotation-config>
declares support for general annotations such as @Required
, @Autowired
, @PostConstruct
, and so on.
<mvc:annotation-driven />
declares explicit support for annotation-driven MVC controllers (i.e. @RequestMapping
, @Controller
, although support for those is the default behaviour), as well as adding support for declarative validation via @Valid
and message body marshalling with @RequestBody
/ResponseBody
.
file_get_contents behind a proxy?
Depending on how the proxy login works stream_context_set_default might help you.
$context = stream_context_set_default(
array(
'http'=>array(
'header'=>'Authorization: Basic ' . base64_encode('username'.':'.'userpass')
)
)
);
$result = file_get_contents('http://..../...');
python requests file upload
If upload_file
is meant to be the file, use:
files = {'upload_file': open('file.txt','rb')}
values = {'DB': 'photcat', 'OUT': 'csv', 'SHORT': 'short'}
r = requests.post(url, files=files, data=values)
and requests
will send a multi-part form POST body with the upload_file
field set to the contents of the file.txt
file.
The filename will be included in the mime header for the specific field:
>>> import requests
>>> open('file.txt', 'wb') # create an empty demo file
<_io.BufferedWriter name='file.txt'>
>>> files = {'upload_file': open('file.txt', 'rb')}
>>> print(requests.Request('POST', 'http://example.com', files=files).prepare().body.decode('ascii'))
--c226ce13d09842658ffbd31e0563c6bd
Content-Disposition: form-data; name="upload_file"; filename="file.txt"
--c226ce13d09842658ffbd31e0563c6bd--
Note the filename="file.txt"
parameter.
You can use a tuple for the files
mapping value, with between 2 and 4 elements, if you need more control. The first element is the filename, followed by the contents, and an optional content-type header value and an optional mapping of additional headers:
files = {'upload_file': ('foobar.txt', open('file.txt','rb'), 'text/x-spam')}
This sets an alternative filename and content type, leaving out the optional headers.
If you are meaning the whole POST body to be taken from a file (with no other fields specified), then don't use the files
parameter, just post the file directly as data
. You then may want to set a Content-Type
header too, as none will be set otherwise. See Python requests - POST data from a file.
How can I display the users profile pic using the facebook graph api?
The returned data is the binary data of the image type. If you use JavaScript to retrieve the user photo, please get the photo data as blob type in a XMLHttpRequest, and then retrieve the blob URL from the response. For your reference:
var request = new XMLHttpRequest;
var photoUri=config.endpoints.graphApiUri + "/v1.0/me/photo/$value";
request.open("GET",photoUri);
request.setRequestHeader("Authorization","Bearer "+token);
request.responseType = "blob";
request.onload = function (){
if(request.readyState == 4 && request.status == 200){
var image = document.createElement("img");
var url = window.URL || window.webkitURL;
var blobUrl = url.createObjectURL(request.response);
image.src = blobUrl;
document.getElementById("UserShow").appendChild(image);
}
};
request.send(null);
How to include a PHP variable inside a MySQL statement
To avoid SQL injection the insert statement with be
$type = 'testing';
$name = 'john';
$description = 'whatever';
$stmt = $con->prepare("INSERT INTO contents (type, reporter, description) VALUES (?, ?, ?)");
$stmt->bind_param("sss", $type , $name, $description);
$stmt->execute();
Passing variables through handlebars partial
This is very possible if you write your own helper. We are using a custom $
helper to accomplish this type of interaction (and more):
/*///////////////////////
Adds support for passing arguments to partials. Arguments are merged with
the context for rendering only (non destructive). Use `:token` syntax to
replace parts of the template path. Tokens are replace in order.
USAGE: {{$ 'path.to.partial' context=newContext foo='bar' }}
USAGE: {{$ 'path.:1.:2' replaceOne replaceTwo foo='bar' }}
///////////////////////////////*/
Handlebars.registerHelper('$', function(partial) {
var values, opts, done, value, context;
if (!partial) {
console.error('No partial name given.');
}
values = Array.prototype.slice.call(arguments, 1);
opts = values.pop();
while (!done) {
value = values.pop();
if (value) {
partial = partial.replace(/:[^\.]+/, value);
}
else {
done = true;
}
}
partial = Handlebars.partials[partial];
if (!partial) {
return '';
}
context = _.extend({}, opts.context||this, _.omit(opts, 'context', 'fn', 'inverse'));
return new Handlebars.SafeString( partial(context) );
});
C# Switch-case string starting with
Short answer: No.
The switch statement takes an expression that is only evaluated once. Based on the result, another piece of code is executed.
So what? => String.StartsWith is a function. Together with a given parameter, it is an expression. However, for your case you need to pass a different parameter for each case, so it cannot be evaluated only once.
Long answer #1 has been given by others.
Long answer #2:
Depending on what you're trying to achieve, you might be interested in the Command Pattern/Chain-of-responsibility pattern. Applied to your case, each piece of code would be represented by an implementation of a Command. In addition to the execute method, the command can provide a boolean Accept method, which checks whether the given string starts with the respective parameter.
Advantage: Instead of your hardcoded switch statement, hardcoded StartsWith evaluations and hardcoded strings, you'd have lot more flexibility.
The example you gave in your question would then look like this:
var commandList = new List<Command>() { new MyABCCommand() };
foreach (Command c in commandList)
{
if (c.Accept(mystring))
{
c.Execute(mystring);
break;
}
}
class MyABCCommand : Command
{
override bool Accept(string mystring)
{
return mystring.StartsWith("abc");
}
}
How to pass an event object to a function in Javascript?
Modify the definition of the function check_me as::
function check_me(ev) {
Now you can access the methods and parameters of the event, in your case:
ev.preventDefault();
Then, you have to pass the parameter on the onclick in the inline call::
<button type="button" onclick="check_me(event);">Click Me!</button>
A useful link to understand this.
Full example:
<!DOCTYPE html>
<html lang="en">
<head>
<script type="text/javascript">
function check_me(ev) {
ev.preventDefault();
alert("Hello World!")
}
</script>
</head>
<body>
<button type="button" onclick="check_me(event);">Click Me!</button>
</body>
</html>
Alternatives (best practices):
Although the above is the direct answer to the question (passing an event object to an inline event), there are other ways of handling events that keep the logic separated from the presentation
A. Using addEventListener
:
<!DOCTYPE html>
<html lang="en">
<head>
</head>
<body>
<button id='my_button' type="button">Click Me!</button>
<!-- put the javascript at the end to guarantee that the DOM is ready to use-->
<script type="text/javascript">
function check_me(ev) {
ev.preventDefault();
alert("Hello World!")
}
<!-- add the event to the button identified #my_button -->
document.getElementById("my_button").addEventListener("click", check_me);
</script>
</body>
</html>
B. Isolating Javascript:
Both of the above solutions are fine for a small project, or a hackish quick and dirty solution, but for bigger projects, it is better to keep the HTML separated from the Javascript.
Just put this two files in the same folder:
<!DOCTYPE html>
<html lang="en">
<head>
</head>
<body>
<button id='my_button' type="button">Click Me!</button>
<!-- put the javascript at the end to guarantee that the DOM is ready to use-->
<script type="text/javascript" src="example.js"></script>
</body>
</html>
function check_me(ev) {
ev.preventDefault();
alert("Hello World!")
}
document.getElementById("my_button").addEventListener("click", check_me);
How to force HTTPS using a web.config file
I was not allowed to install URL Rewrite in my environment, so, I found another path.
Adding this to my web.config added the error rewrite and worked on IIS 7.5:
<system.webServer>
<httpErrors errorMode="Custom" defaultResponseMode="File" defaultPath="C:\WebSites\yoursite\" >
<remove statusCode="403" subStatusCode="4" />
<error statusCode="403" subStatusCode="4" responseMode="File" path="redirectToHttps.html" />
</httpErrors>
Then, following the advice here: https://www.sslshopper.com/iis7-redirect-http-to-https.html
I configured the IIS website to require SSL and created the html file that does the redirect (redirectToHttps.html) upon the 403 (Forbidden) error:
<html>
<head><title>Redirecting...</title></head>
<script language="JavaScript">
function redirectHttpToHttps()
{
var httpURL= window.location.hostname + window.location.pathname + window.location.search;
var httpsURL= "https://" + httpURL;
window.location = httpsURL;
}
redirectHttpToHttps();
</script>
<body>
</body>
</html>
I hope someone finds this useful as I could not find all of the pieces in one place anywhere else.