weird_for.c

// I'm going to hell for this one...
//
// https://godbolt.org/z/PjxjveaG4
#include <stdbool.h>
#include <stddef.h>

#ifdef __clang__
#define typeof(x) __typeof__(x)
#endif

// extract
#define _ITER__TYPENAME(a, b, c, d, e, ...) a
#define _ITER__COND(a, b, c, d, e, ...)     b
#define _ITER__NEXT(a, b, c, d, e, ...)     c
#define _ITER__ITERATOR(a, b, c, d, e, ...) d
#define _ITER__ENDPOINT(a, b, c, d, e, ...) e
#define _ITER__REST(a, b, c, d, e, ...)     , ## __VA_ARGS__

// lmao
#define for(a, b)                                 \
    for (_ITER__TYPENAME b a = _ITER__ITERATOR b, \
    __end  = _ITER__ENDPOINT b;                   \
    _ITER__COND b (a, __end _ITER__REST b);       \
    _ITER__NEXT b (&a _ITER__REST b))

//////////////////////////////////////
// Range based iterator
//////////////////////////////////////
inline static bool range_cond(int it, int end) { return it < end; }
inline static void range_next(int* it) { *it += 1; }
#define RANGE(min, max) (int, range_cond, range_next, min, max)

//////////////////////////////////////
// Array iterator
//////////////////////////////////////
inline static bool array_cond(void* it, void* end, size_t stride) { return it != end; }
inline static void array_next(void** it, size_t stride) { char** ptr = (char**)it; *ptr += stride; }
#define ARRAY(arr, n) (typeof(arr), array_cond, array_next, arr, &arr[n], sizeof(*arr))

//////////////////////////////////////
// C string iterator
//////////////////////////////////////
inline static bool cstr_cond(char* it, char* end) { return *it != 0; }
inline static void cstr_next(char** it) { *it += 1; }
#define CSTR(arr) (const char*, cstr_cond, cstr_next, arr, 0)

int foo(int n, int* arr) {
    int sum = 0;
    for (i, RANGE(0, n)) sum += arr[i];
    return sum;
}

int bar(int n, int* arr) {
    int sum = 0;
    for (p, ARRAY(arr, n)) sum += *p;
    return sum;
}

int baz(int n, const char* str) {
    int sum = 0;
    for (c, CSTR(str)) sum += *c;
    return sum;
}