1 files changed, 105 insertions, 0 deletions
diff --git a/misc/examples/algo/coroutines.c b/misc/examples/algo/coroutines.c
new file mode 100644
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+++ b/misc/examples/algo/coroutines.c
@@ -0,0 +1,105 @@
+#include <stc/algo/coroutine.h>
+#include <stdio.h>
+#include <stdint.h>
+
+// Demonstrate to call another coroutine from a coroutine:
+// First create prime generator, then call fibonacci sequence:
+
+bool is_prime(int64_t i) {
+    for (int64_t j=2; j*j <= i; ++j)
+        if (i % j == 0) return false;
+    return true;
+}
+
+struct prime {
+    int count, idx;
+    int64_t result, pos;
+    int cco_state;
+};
+
+bool prime(struct prime* U) {
+    cco_begin(U);
+        if (U->result < 2) U->result = 2;
+        if (U->result == 2) {
+            if (U->count-- == 0) cco_return;
+            ++U->idx;
+            cco_yield(true);
+        }
+        U->result += !(U->result & 1);
+        for (U->pos = U->result; U->count > 0; U->pos += 2) {
+            if (is_prime(U->pos)) {
+                --U->count;
+                ++U->idx;
+                U->result = U->pos;
+                cco_yield(true);
+            }
+        }
+        cco_final:
+            printf("final prm\n");
+    cco_end(false);
+}
+
+
+// Use coroutine to create a fibonacci sequence generator:
+
+struct fibonacci {
+    int count, idx;
+    int64_t result, b;
+    int cco_state;
+};
+
+bool fibonacci(struct fibonacci* F) {
+    assert(F->count < 94);
+
+    cco_begin(F);
+        F->idx = 0;
+        F->result = 0;
+        F->b = 1;
+        for (;;) {
+            if (F->count-- == 0)
+                cco_return;
+            if (++F->idx > 1) {
+                int64_t sum = F->result + F->b; // NB! locals only lasts until next cco_yield!
+                F->result = F->b;
+                F->b = sum;
+            }
+            cco_yield(true);
+        }
+        cco_final:
+            printf("final fib\n");
+    cco_end(false);
+}
+
+// Combine
+
+struct combined {
+    struct prime prm;
+    struct fibonacci fib;
+    int cco_state;
+};
+
+bool combined(struct combined* C) {
+    cco_begin(C);
+        cco_yield(prime(&C->prm), &C->prm, true);
+        cco_yield(fibonacci(&C->fib), &C->fib, true);
+
+        // Reuse the C->prm context and extend the count:
+        C->prm.count = 8; C->prm.result += 2;
+        cco_yield(prime(&C->prm), &C->prm, true);
+
+        cco_final: puts("final comb");
+    cco_end(false);
+}
+
+int main(void) {
+    struct combined comb = {.prm={.count=8}, .fib={14}};
+    if (true)
+        while (combined(&comb))
+            printf("Prime(%d)=%lld, Fib(%d)=%lld\n", 
+                comb.prm.idx, (long long)comb.prm.result, 
+                comb.fib.idx, (long long)comb.fib.result);
+    else
+        while (prime(&comb.prm))
+            printf("Prime(%d)=%lld\n", 
+                comb.prm.idx, (long long)comb.prm.result);
+}