c - Include a file multiple times with different macros -


i got file contains generic methods working arrays of different number types (the basic ideas described in pseudo-generics in c). type can specified setting type macro. looks (just part of it):

array_analyzers.c:

#ifndef type #error type isn't defined #endif  #define concat(x, y) x ## y #define get_name(base, type) concat(base, type)  type get_name(get_minimum_, type) (type nums[static 1], int len){     type min = nums[0];      (int = 1; < len; i++) {         if (nums[i] < min) {             min = nums[i];         }     }      return min; }  #undef concat #undef get_name #undef type

now, created header file looks this:

array_analyzers.h:

#ifndef type #error type isn't defined #endif  #define concat(x, y) x ## y #define get_name(base, type) concat(base, type)  type get_name(get_minimum_, type) (type nums[static 1], int len);  #undef concat #undef get_name #undef type

finally, want use main.c:

#include <stdio.h>  #define type int #include "array_analyzers.h" #define type double #include "array_analyzers.h"  int main(void){   int nums[] = {1, 2, 3};   printf("%i\n", get_minimum_int(nums, 3)); }

however, i'm getting following error message:

array_analyzers.c:2:2: error: #error type isn't defined

what wrong here? works when run preprocessor first , create separate files right contents, awful.

you don not declare int in loop @ beginning of scope, in loop. if using gcc can add -std=c99 compiler option accept code.

in function standard loop should alway accepted. in function int declared @ beginning of scope.

int ansi_c (){     int i;     ( = 0 ; < 10; i++ ){      } }

and in function loop accepted when -std=c99 or std=gnu99 added. function declares int inside loop.

c99(){     (int = 0; < 10; i++ ){      } }

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