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// https://quuxplusone.github.io/blog/2019/03/06/pythagorean-triples/
#include <stdio.h>
#include <stc/coroutine.h>
#include <stc/algorithm.h>
typedef struct {
int max_triples;
int a, b, c;
} Triple;
// Create an iterable generator over Triple with count items.
// Requires coroutine Triple_next() and function Triple_begin() to be defined.
cco_iter_struct(Triple,
int count;
);
int Triple_next(Triple_iter* it) {
Triple* g = it->ref; // note: before cco_routine
cco_routine(it)
{
for (g->c = 5;; ++g->c) {
for (g->a = 1; g->a < g->c; ++g->a) {
for (g->b = g->a; g->b < g->c; ++g->b) {
if (g->a*g->a + g->b*g->b == g->c*g->c) {
if (it->count++ == g->max_triples)
cco_return;
cco_yield();
}
}
}
}
cco_final:
it->ref = NULL; // stop the iterator
}
return 0;
}
Triple_iter Triple_begin(Triple* g) {
Triple_iter it = {.ref=g};
Triple_next(&it);
return it;
}
int main(void)
{
puts("Pythagorean triples.\nGet max 200 triples with c < 50:");
Triple triple = {.max_triples=200};
c_foreach (i, Triple, triple) {
if (i.ref->c < 50)
printf("%u: (%d, %d, %d)\n", i.count, i.ref->a, i.ref->b, i.ref->c);
else
cco_stop(&i);
}
puts("\nGet the 10 first triples with odd a's and a <= 20:");
c_forfilter (i, Triple, triple,
i.ref->a <= 20 &&
(i.ref->a & 1) &&
c_flt_take(i, 10)
){
printf("%d: (%d, %d, %d)\n", c_flt_getcount(i), i.ref->a, i.ref->b, i.ref->c);
}
}
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