1 files changed, 69 insertions, 0 deletions
diff --git a/cpp/037call_reply.cc b/cpp/037call_reply.cc
new file mode 100644
index 00000000..9e62c1da
--- /dev/null
+++ b/cpp/037call_reply.cc
@@ -0,0 +1,69 @@
+//: Calls can also generate products, using 'reply'.
+
+:(scenario reply)
+recipe main [
+  3:integer, 4:integer <- f 2:literal
+]
+recipe f [
+  12:integer <- next-ingredient
+  13:integer <- add 1:literal, 12:integer
+  reply 12:integer, 13:integer
+]
++run: instruction main/0
++run: result 0 is 2
++mem: storing 2 in location 3
++run: result 1 is 3
++mem: storing 3 in location 4
+
+:(before "End Primitive Recipe Declarations")
+REPLY,
+:(before "End Primitive Recipe Numbers")
+Recipe_number["reply"] = REPLY;
+:(before "End Primitive Recipe Implementations")
+case REPLY: {
+  vector<vector<int> > callee_results;
+  for (size_t i = 0; i < current_instruction().ingredients.size(); ++i) {
+    callee_results.push_back(read_memory(current_instruction().ingredients[i]));
+  }
+  Current_routine->calls.pop();
+  assert(!Current_routine->calls.empty());
+  const instruction& caller_instruction = current_instruction();
+  assert(caller_instruction.products.size() <= callee_results.size());
+  for (size_t i = 0; i < caller_instruction.products.size(); ++i) {
+    trace("run") << "result " << i << " is " << to_string(callee_results[i]);
+    write_memory(caller_instruction.products[i], callee_results[i]);
+  }
+  break;  // instruction loop will increment caller's step_index
+}
+
+//: Products can include containers and exclusive containers, addresses and arrays.
+:(scenario reply_container)
+recipe main [
+  3:point <- f 2:literal
+]
+recipe f [
+  12:integer <- next-ingredient
+  13:integer <- copy 35:literal
+  reply 12:point
+]
++run: instruction main/0
++run: result 0 is [2, 35]
++mem: storing 2 in location 3
++mem: storing 35 in location 4
+
+:(code)
+string to_string(const vector<int>& in) {
+  if (in.empty()) return "[]";
+  ostringstream out;
+  if (in.size() == 1) {
+    out << in[0];
+    return out.str();
+  }
+  out << "[";
+  for (size_t i = 0; i < in.size(); ++i) {
+    if (i > 0) out << ", ";
+    out << in[i];
+  }
+  out << "]";
+  return out.str();
+}