1 files changed, 105 insertions, 0 deletions
diff --git a/035call.cc b/035call.cc
new file mode 100644
index 00000000..2cb40af8
--- /dev/null
+++ b/035call.cc
@@ -0,0 +1,105 @@
+//: So far the recipes we define can't run each other. Let's fix that.
+
+:(scenario calling_recipe)
+recipe main [
+  f
+]
+recipe f [
+  3:integer <- add 2:literal, 2:literal
+]
++mem: storing 4 in location 3
+
+:(scenario return_on_fallthrough)
+recipe main [
+  f
+  1:integer <- copy 34:literal
+  2:integer <- copy 34:literal
+  3:integer <- copy 34:literal
+]
+recipe f [
+  4:integer <- copy 34:literal
+  5:integer <- copy 34:literal
+]
++run: instruction main/0
++run: instruction f/0
++run: instruction f/1
++run: instruction main/1
++run: instruction main/2
++run: instruction main/3
+
+:(before "struct routine {")
+// Everytime a recipe runs another, we interrupt it and start running the new
+// recipe. When that finishes, we continue this one where we left off.
+// This requires maintaining a 'stack' of interrupted recipes or 'calls'.
+struct call {
+  recipe_number running_recipe;
+  index_t running_step_index;
+  // End call Fields
+  call(recipe_number r) :running_recipe(r), running_step_index(0) {}
+};
+typedef stack<call> call_stack;
+
+:(replace{} "struct routine")
+struct routine {
+  call_stack calls;
+  // End routine Fields
+  routine(recipe_number r);
+  bool completed() const;
+  const vector<instruction>& steps() const;
+};
+:(code)
+routine::routine(recipe_number r) {
+  calls.push(call(r));
+  // End routine Constructor
+}
+
+//:: now update routine's helpers
+
+:(replace{} "inline index_t& current_step_index()")
+inline index_t& current_step_index() {
+  return Current_routine->calls.top().running_step_index;
+}
+:(replace{} "inline const string& current_recipe_name()")
+inline const string& current_recipe_name() {
+  return Recipe[Current_routine->calls.top().running_recipe].name;
+}
+:(replace{} "inline const instruction& current_instruction()")
+inline const instruction& current_instruction() {
+  return Recipe[Current_routine->calls.top().running_recipe].steps[Current_routine->calls.top().running_step_index];
+}
+
+:(replace{} "default:" following "End Primitive Recipe Implementations")
+default: {
+  // not a primitive; try to look up the book of recipes
+  if (Recipe.find(current_instruction().operation) == Recipe.end()) {
+    raise << "undefined operation " << current_instruction().operation << ": " << current_instruction().name << '\n';
+    break;
+  }
+  Current_routine->calls.push(call(current_instruction().operation));
+  continue;  // not done with caller; don't increment current_step_index()
+}
+
+//:: finally, we need to fix the termination conditions for the run loop
+
+:(replace{} "inline bool routine::completed() const")
+inline bool routine::completed() const {
+  return calls.empty();
+}
+
+inline const vector<instruction>& routine::steps() const {
+  return Recipe[calls.top().running_recipe].steps;
+}
+
+:(before "Running One Instruction")
+// when we reach the end of one call, we may reach the end of the one below
+// it, and the one below that, and so on
+while (current_step_index() >= Current_routine->steps().size()) {
+  Current_routine->calls.pop();
+  if (Current_routine->calls.empty()) return;
+  // todo: no results returned warning
+  ++current_step_index();
+}
+
+:(before "End Includes")
+#include <stack>
+using std::stack;