1 files changed, 75 insertions, 0 deletions
diff --git a/misc/examples/coroutines/triples.c b/misc/examples/coroutines/triples.c
new file mode 100644
index 00000000..d6ce2791
--- /dev/null
+++ b/misc/examples/coroutines/triples.c
@@ -0,0 +1,75 @@
+// https://quuxplusone.github.io/blog/2019/03/06/pythagorean-triples/
+
+#include <stdio.h>
+#include <stc/coroutine.h>
+
+void triples_vanilla(int max_c) {
+    for (int c = 5, i = 0;; ++c) {
+        for (int a = 1; a < c; ++a) {
+            for (int b = a + 1; b < c; ++b) {
+                if ((int64_t)a*a + (int64_t)b*b == (int64_t)c*c) {
+                    if (c > max_c)
+                        goto done;
+                    printf("%d: {%d, %d, %d}\n", ++i, a, b, c);
+                }
+            }
+        }
+    }
+    done:;
+}
+
+struct triples {
+    int max_c;
+    int a, b, c;
+    int cco_state;
+};
+
+int triples_coro(struct triples* t) {
+    cco_routine(t) {
+        for (t->c = 5;; ++t->c) {
+            for (t->a = 1; t->a < t->c; ++t->a) {
+                for (t->b = t->a + 1; t->b < t->c; ++t->b) {
+                    if ((int64_t)t->a * t->a +
+                        (int64_t)t->b * t->b ==
+                        (int64_t)t->c * t->c)
+                    {
+                        if (t->c > t->max_c)
+                            cco_return;
+                        cco_yield();
+                    }
+                }
+            }
+        }
+        cco_final:
+        puts("done");
+    }
+    return 0;
+}
+
+int gcd(int a, int b) {
+    while (b) {
+        int t = a % b;
+        a = b;
+        b = t;
+    }
+    return a;
+}
+
+int main(void)
+{
+    puts("Vanilla triples:");
+    triples_vanilla(20);
+
+    puts("\nCoroutine triples with GCD = 1:");
+    struct triples t = {.max_c = 100};
+    int n = 0;
+
+    cco_blocking_call(triples_coro(&t)) {
+        if (gcd(t.a, t.b) > 1)
+            continue;
+        if (++n <= 20)
+            printf("%d: {%d, %d, %d}\n", n, t.a, t.b, t.c);
+        else
+            cco_stop(&t);
+    }
+}