WrongWay reversible iterator Copyright(C) 2016 Henry Kroll III www.thenerdshow.com, C (gcc)

WrongWay reversible iterator Copyright(C) 2016 Henry Kroll III www.thenerdshow.com

//WrongWay reversible iterator Copyright(C) 2016 Henry Kroll III www.thenerdshow.com
#include <stdio.h>
typedef float some;
typedef struct {
    size_t pos, start, end;
    some *ptr;
    some *(*next)(piter);
} iter, *piter;
//iterator next
some *next (piter i) {
    return i->pos <= i->end? &i->ptr[i->pos++] : NULL;
}
//iterator previous
some *prev (piter i) {
    return i->pos >= i->start? &i->ptr[i->pos--] : NULL;
}
//shortcuts
#define ITER(name, start, end) &(iter){start, start, end, name, &next}
#define FOREACH(i, j) for (some *j;(j = i->next(i));)
#define NEXT(i) *i->next(i)
#define REVERSE(i) { if(i->pos>i->start){i->next = prev, i->pos=i->end;}\
                   else{ i->next = next, i->pos = i->start;}}while(0)
int main (void) {
    some i[]={0.0, 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0}; 
    //wrap i in an iterator kind of like python's iter()
    piter k = ITER(i, 2, 6);
    printf ("%1.2f\n", NEXT(k));
    printf ("%1.2f\n", NEXT(k));
    FOREACH (k, j) printf ("%1.2f ", *j);
    REVERSE(k); putchar ('\n');
    FOREACH (k, j) printf ("%1.2f ", *j);
    REVERSE(k); putchar ('\n');
    FOREACH (k, j) printf ("%1.2f ", *j);
    REVERSE(k); putchar ('\n');
    printf ("%1.2f\n", NEXT(k));
    printf ("%1.2f\n", NEXT(k));
    printf ("%1.2f\n", NEXT(k));
    printf ("%1.2f\n", NEXT(k));
    return 0;
}


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