C language Implements anonymous functions

The anonymous function can be implemented in the C language by means of a macro definition, as follows:

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#define lambda(return_type, function_body) \({ \      return_type $thisfunction_body \          $this; \})#define $ lambda

The definition takes advantage of GCC's expansion of the C language (a block of code wrapped up in braces can return a value), a macro definition that returns $this (function pointers), and if we need a function that returns two integers, we can also encapsulate the macro again as follows:

1	#define add2int(function_body) $(int, (int _a, int _b){function_body})

Then we can use the macro as follows (for all elements of an integer array):

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int sum(int *arr, int length, int (*add)(int, int));int main(int argc, char **argv){    int arr[] = { [0 ... 9] = 1, [10 ... 89] = 2, [90 ... 99] = 3 };    int ret = sum(arr, sizeof(arr)/sizeof(int), add2int(int c = _a + _b; return c;));    //add2int返回一个求两个整数和的函数    printf("sum of arr is %d\n", ret);}int sum(int *arr, int length, int (*add)(int, int)){    int sum = 0;    for (int i=0; i < length; i++)    {        sum = add(sum, arr[i]);    }    return sum;}

Of course, you can also use the Lambda macro directly, note that Function_body needs to include the return type of the function and the argument list, replacing the 6th line of code with:

1234	int ret = SUM (arr, sizeof (arr)/ sizeof ( int Code class= "CPP Color1 bold" >int int Code class= "CPP Plain" >_a, int _b) { Code class= "CPP Spaces" >     int c = _a + _b;      return C;

Of course such code is certainly inefficient, and superfluous, here is just a simple example

From for notes (Wiz)

C language Implements anonymous functions