How to make inline functions in C

Question

I m using Linq To XML  new XElement  Prefix   Prefix    null        Prefix    but I want to do some computation to the prefix before adding it to the xml  like eliminating spaces  special chars  some calculations etc   I don t want to create functions because this ones won t be of any help on any other part of my program but this  so is there any way to create inline functions

User · Answer

The answer to your question is yes and no, depending on what you mean by "inline function". If you're using the term like it's used in C++ development then the answer is no, you can't do that - even a lambda expression is a function call. While it's true that you can define inline lambda expressions to replace function declarations in C#, the compiler still ends up creating an anonymous function.

Here's some really simple code I used to test this (VS2015):

    static void Main(string[] args)
    {
        Func<int, int> incr = a => a + 1;
        Console.WriteLine($"P1 = {incr(5)}");
    }

What does the compiler generate? I used a nifty tool called ILSpy that shows the actual IL assembly generated. Have a look (I've omitted a lot of class setup stuff)

This is the Main function:

        IL_001f: stloc.0
        IL_0020: ldstr "P1 = {0}"
        IL_0025: ldloc.0
        IL_0026: ldc.i4.5
        IL_0027: callvirt instance !1 class [mscorlib]System.Func`2<int32, int32>::Invoke(!0)
        IL_002c: box [mscorlib]System.Int32
        IL_0031: call string [mscorlib]System.String::Format(string, object)
        IL_0036: call void [mscorlib]System.Console::WriteLine(string)
        IL_003b: ret

See those lines IL_0026 and IL_0027? Those two instructions load the number 5 and call a function. Then IL_0031 and IL_0036 format and print the result.

And here's the function called:

        .method assembly hidebysig 
            instance int32 '<Main>b__0_0' (
                int32 a
            ) cil managed 
        {
            // Method begins at RVA 0x20ac
            // Code size 4 (0x4)
            .maxstack 8

            IL_0000: ldarg.1
            IL_0001: ldc.i4.1
            IL_0002: add
            IL_0003: ret
        } // end of method '<>c'::'<Main>b__0_0'

It's a really short function, but it is a function.

Is this worth any effort to optimize? Nah. Maybe if you're calling it thousands of times a second, but if performance is that important then you should consider calling native code written in C/C++ to do the work.

In my experience readability and maintainability are almost always more important than optimizing for a few microseconds gain in speed. Use functions to make your code readable and to control variable scoping and don't worry about performance.

"Premature optimization is the root of all evil (or at least most of it) in programming." -- Donald Knuth

"A program that doesn't run correctly doesn't need to run fast" -- Me

User · Answer

You can use Func which encapsulates a method that has one parameter and returns a value of the type specified by the TResult parameter   void Method         Func lt string string gt  inlineFunction   source   gt                    add your functionality here         return source                    call the inline function    inlineFunction  prefix

User · Answer

Not only Inside methods  it can be used inside classes also   class Calculator               public static int Sum int x int y    gt  x   y          public static Func lt int  int  int gt   Add    x  y    gt  x   y          public static Action lt int int gt  DisplaySum    x  y    gt  Console WriteLine x   y

User · Answer

Yes   You can create anonymous methods or lambda expressions   Func lt string  string gt  PrefixTrimmer   delegate string x        return x           Func lt string  string gt  PrefixTrimmer   x   gt  x

User · Answer

C  7 adds support for local functions  Here is the previous example using a local function  void Method         string localFunction string source                   add your functionality here         return source                 call the inline function    localFunction  prefix

User · Answer

Yes  C  supports that  There are several syntaxes available    Anonymous methods were added in C  2 0   Func lt int  int  int gt  add   delegate int x  int y        return x   y     Action lt int gt  print   delegate int x        Console WriteLine x     Action lt int gt  helloWorld   delegate    parameters can be elided if ignored       Console WriteLine  Hello world        Lambdas are new in C  3 0 and come in two flavours    Expression lambdas   Func lt int  int  int gt  add    int x  int y    gt  x   y     or    Func lt int  int  int gt  add    x  y    gt  x   y     types are inferred by the compiler  Statement lambdas   Action lt int gt  print    int x    gt    Console WriteLine x      Action lt int gt  print   x   gt    Console WriteLine x         inferred types Func lt int  int  int gt  add    x  y    gt    return x   y       Local functions have been introduced with C  7 0   int add int x  int y    gt  x   y  void print int x    Console WriteLine x        There are basically two different types for these  Func and Action  Funcs return values but Actions don t  The last type parameter of a Func is the return type  all the others are the parameter types   There are similar types with different names  but the syntax for declaring them inline is the same  An example of this is Comparison lt T gt   which is roughly equivalent to Func lt T  T  int gt    Func lt string  string  int gt  compare1    l r    gt  1  Comparison lt string gt  compare2    l  r    gt  1  Comparison lt string gt  compare3   compare1     this one only works from C  4 0 onwards   These can be invoked directly as if they were regular methods   int x   add 23  17      x    40 print x      outputs 40 helloWorld x      helloWorld has one int parameter declared  Action lt int gt                    even though it does not make any use of it

[c#] How to make inline functions in C#

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