3656

Periodic cleanup to replace 'reply' with 'return' everywhere in the
repo.

I use 'reply' for students to help reinforce the metaphor of function
calls as being like messages through a pipe. But that causes 'reply' to
get into my muscle memory when writing Mu code for myself, and I worry
that that makes Mu seem unnecessarily alien to anybody reading on
Github.

Perhaps I should just give it up? I'll try using 'return' with my next
student.

1 files changed, 173 insertions, 0 deletions

diff --git a/028call_return.cc b/028call_return.cc
new file mode 100644
index 00000000..436f4751
--- /dev/null
+++ b/028call_return.cc
@@ -0,0 +1,173 @@
+//: Calls can also generate products, using 'reply' or 'return'.
+
+:(scenario return)
+def main [
+  1:num, 2:num <- f 34
+]
+def f [
+  12:num <- next-ingredient
+  13:num <- add 1, 12:num
+  return 12:num, 13:num
+]
++mem: storing 34 in location 1
++mem: storing 35 in location 2
+
+:(scenario reply)
+def main [
+  1:num, 2:num <- f 34
+]
+def f [
+  12:num <- next-ingredient
+  13:num <- add 1, 12:num
+  reply 12:num, 13:num
+  $dump-trace
+]
++mem: storing 34 in location 1
++mem: storing 35 in location 2
+
+:(before "End Primitive Recipe Declarations")
+RETURN,
+:(before "End Primitive Recipe Numbers")
+put(Recipe_ordinal, "return", RETURN);
+put(Recipe_ordinal, "reply", RETURN);  // synonym while teaching
+:(before "End Primitive Recipe Checks")
+case RETURN: {
+  break;  // checks will be performed by a transform below
+}
+:(before "End Primitive Recipe Implementations")
+case RETURN: {
+  // Starting Reply
+  if (Trace_stream) {
+    trace(9999, "trace") << current_instruction().name << ": decrementing callstack depth from " << Trace_stream->callstack_depth << end();
+    --Trace_stream->callstack_depth;
+    if (Trace_stream->callstack_depth < 0) {
+      Current_routine->calls.clear();
+      goto stop_running_current_routine;
+    }
+  }
+  Current_routine->calls.pop_front();
+  // just in case 'main' returns a value, drop it for now
+  if (Current_routine->calls.empty()) goto stop_running_current_routine;
+  for (int i = 0;  i < SIZE(ingredients);  ++i)
+    trace(9998, "run") << "result " << i << " is " << to_string(ingredients.at(i)) << end();
+  // make return products available to caller
+  copy(ingredients.begin(), ingredients.end(), inserter(products, products.begin()));
+  // End Reply
+  break;  // continue to process rest of *caller* instruction
+}
+
+//: Types in return instructions are checked ahead of time.
+
+:(before "End Checks")
+Transform.push_back(check_types_of_return_instructions);  // idempotent
+:(code)
+void check_types_of_return_instructions(const recipe_ordinal r) {
+  const recipe& caller = get(Recipe, r);
+  trace(9991, "transform") << "--- check types of return instructions in recipe " << caller.name << end();
+  for (int i = 0;  i < SIZE(caller.steps);  ++i) {
+    const instruction& caller_instruction = caller.steps.at(i);
+    if (caller_instruction.is_label) continue;
+    if (caller_instruction.products.empty()) continue;
+    if (caller_instruction.operation < MAX_PRIMITIVE_RECIPES) continue;
+    const recipe& callee = get(Recipe, caller_instruction.operation);
+    for (int i = 0;  i < SIZE(callee.steps);  ++i) {
+      const instruction& return_inst = callee.steps.at(i);
+      if (return_inst.operation != RETURN) continue;
+      // check types with the caller
+      if (SIZE(caller_instruction.products) > SIZE(return_inst.ingredients)) {
+        raise << maybe(caller.name) << "too few values returned from " << callee.name << '\n' << end();
+        break;
+      }
+      for (int i = 0;  i < SIZE(caller_instruction.products);  ++i) {
+        reagent/*copy*/ lhs = return_inst.ingredients.at(i);
+        reagent/*copy*/ rhs = caller_instruction.products.at(i);
+        // End Check RETURN Copy(lhs, rhs)
+        if (!types_coercible(rhs, lhs)) {
+          raise << maybe(callee.name) << return_inst.name << " ingredient '" << lhs.original_string << "' can't be saved in '" << rhs.original_string << "'\n" << end();
+          raise << "  ['" << to_string(lhs.type) << "' vs '" << to_string(rhs.type) << "']\n" << end();
+          goto finish_return_check;
+        }
+      }
+      // check that any return ingredients with /same-as-ingredient connect up
+      // the corresponding ingredient and product in the caller.
+      for (int i = 0;  i < SIZE(caller_instruction.products);  ++i) {
+        if (has_property(return_inst.ingredients.at(i), "same-as-ingredient")) {
+          string_tree* tmp = property(return_inst.ingredients.at(i), "same-as-ingredient");
+          if (!tmp || !tmp->atom) {
+            raise << maybe(caller.name) << "'same-as-ingredient' metadata should take exactly one value in '" << to_original_string(return_inst) << "'\n" << end();
+            goto finish_return_check;
+          }
+          int ingredient_index = to_integer(tmp->value);
+          if (ingredient_index >= SIZE(caller_instruction.ingredients)) {
+            raise << maybe(caller.name) << "too few ingredients in '" << to_original_string(caller_instruction) << "'\n" << end();
+            goto finish_return_check;
+          }
+          if (!is_dummy(caller_instruction.products.at(i)) && !is_literal(caller_instruction.ingredients.at(ingredient_index)) && caller_instruction.products.at(i).name != caller_instruction.ingredients.at(ingredient_index).name) {
+            raise << maybe(caller.name) << "'" << to_original_string(caller_instruction) << "' should write to '" << caller_instruction.ingredients.at(ingredient_index).original_string << "' rather than '" << caller_instruction.products.at(i).original_string << "'\n" << end();
+          }
+        }
+      }
+      finish_return_check:;
+    }
+  }
+}
+
+:(scenario return_type_mismatch)
+% Hide_errors = true;
+def main [
+  3:num <- f 2
+]
+def f [
+  12:num <- next-ingredient
+  13:num <- copy 35
+  14:point <- copy 12:point/raw
+  return 14:point
+]
++error: f: return ingredient '14:point' can't be saved in '3:num'
+
+//: In Mu we'd like to assume that any instruction doesn't modify its
+//: ingredients unless they're also products. The /same-as-ingredient inside
+//: the recipe's 'return' indicates that an ingredient is intended to be
+//: modified in place, and will help catch accidental misuse of such
+//: 'ingredient-products' (sometimes called in-out parameters in other
+//: languages).
+
+:(scenario return_same_as_ingredient)
+% Hide_errors = true;
+def main [
+  1:num <- copy 0
+  2:num <- test1 1:num  # call with different ingredient and product
+]
+def test1 [
+  10:num <- next-ingredient
+  return 10:num/same-as-ingredient:0
+]
++error: main: '2:num <- test1 1:num' should write to '1:num' rather than '2:num'
+
+:(scenario return_same_as_ingredient_dummy)
+def main [
+  1:num <- copy 0
+  _ <- test1 1:num  # call with different ingredient and product
+]
+def test1 [
+  10:num <- next-ingredient
+  return 10:num/same-as-ingredient:0
+]
+$error: 0
+
+:(code)
+string to_string(const vector<double>& in) {
+  if (in.empty()) return "[]";
+  ostringstream out;
+  if (SIZE(in) == 1) {
+    out << no_scientific(in.at(0));
+    return out.str();
+  }
+  out << "[";
+  for (int i = 0;  i < SIZE(in);  ++i) {
+    if (i > 0) out << ", ";
+    out << no_scientific(in.at(i));
+  }
+  out << "]";
+  return out.str();
+}