1 //: Calls can also generate products, using 'reply' or 'return'.
  2 
  3 :(scenario return)
  4 def main [
  5   1:num, 2:num <- f 34
  6 ]
  7 def f [
  8   12:num <- next-ingredient
  9   13:num <- add 1, 12:num
 10   return 12:num, 13:num
 11 ]
 12 +mem: storing 34 in location 1
 13 +mem: storing 35 in location 2
 14 
 15 :(scenario reply)
 16 def main [
 17   1:num, 2:num <- f 34
 18 ]
 19 def f [
 20   12:num <- next-ingredient
 21   13:num <- add 1, 12:num
 22   reply 12:num, 13:num
 23 ]
 24 +mem: storing 34 in location 1
 25 +mem: storing 35 in location 2
 26 
 27 :(before "End Primitive Recipe Declarations")
 28 RETURN,
 29 :(before "End Primitive Recipe Numbers")
 30 put(Recipe_ordinal, "return", RETURN);
 31 put(Recipe_ordinal, "reply", RETURN);  // synonym while teaching
 32 put(Recipe_ordinal, "output", RETURN);  // experiment
 33 :(before "End Primitive Recipe Checks")
 34 case RETURN: {
 35   break;  // checks will be performed by a transform below
 36 }
 37 :(before "End Primitive Recipe Implementations")
 38 case RETURN: {
 39   // Begin Return
 40   if (Trace_stream) {
 41     trace("trace") << current_instruction().name << ": decrementing callstack depth from " << Trace_stream->callstack_depth << end();
 42     --Trace_stream->callstack_depth;
 43     if (Trace_stream->callstack_depth < 0) {
 44       Current_routine->calls.clear();
 45       goto stop_running_current_routine;
 46     }
 47   }
 48   Current_routine->calls.pop_front();
 49   // just in case 'main' returns a value, drop it for now
 50   if (Current_routine->calls.empty()) goto stop_running_current_routine;
 51   for (int i = 0;  i < SIZE(ingredients);  ++i)
 52     trace(9998, "run") << "result " << i << " is " << to_string(ingredients.at(i)) << end();
 53   // make return products available to caller
 54   copy(ingredients.begin(), ingredients.end(), inserter(products, products.begin()));
 55   // End Return
 56   break;  // continue to process rest of *caller* instruction
 57 }
 58 
 59 //: Types in return instructions are checked ahead of time.
 60 
 61 :(before "End Checks")
 62 Transform.push_back(check_types_of_return_instructions);  // idempotent
 63 :(code)
 64 void check_types_of_return_instructions(const recipe_ordinal r) {
 65   const recipe& caller = get(Recipe, r);
 66   trace(9991, "transform") << "--- check types of return instructions in recipe " << caller.name << end();
 67   for (int i = 0;  i < SIZE(caller.steps);  ++i) {
 68     const instruction& caller_instruction = caller.steps.at(i);
 69     if (caller_instruction.is_label) continue;
 70     if (caller_instruction.products.empty()) continue;
 71     if (is_primitive(caller_instruction.operation)) continue;
 72     const recipe& callee = get(Recipe, caller_instruction.operation);
 73     for (int i = 0;  i < SIZE(callee.steps);  ++i) {
 74       const instruction& return_inst = callee.steps.at(i);
 75       if (return_inst.operation != RETURN) continue;
 76       // check types with the caller
 77       if (SIZE(caller_instruction.products) > SIZE(return_inst.ingredients)) {
 78         raise << maybe(caller.name) << "too few values returned from " << callee.name << '\n' << end();
 79         break;
 80       }
 81       for (int i = 0;  i < SIZE(caller_instruction.products);  ++i) {
 82         reagent/*copy*/ lhs = return_inst.ingredients.at(i);
 83         reagent/*copy*/ rhs = caller_instruction.products.at(i);
 84         // End Check RETURN Copy(lhs, rhs)
 85         if (!types_coercible(rhs, lhs)) {
 86           raise << maybe(callee.name) << return_inst.name << " ingredient '" << lhs.original_string << "' can't be saved in '" << rhs.original_string << "'\n" << end();
 87           raise << "  ['" << to_string(lhs.type) << "' vs '" << to_string(rhs.type) << "']\n" << end();
 88           goto finish_return_check;
 89         }
 90       }
 91       // check that any return ingredients with /same-as-ingredient connect up
 92       // the corresponding ingredient and product in the caller.
 93       for (int i = 0;  i < SIZE(caller_instruction.products);  ++i) {
 94         if (has_property(return_inst.ingredients.at(i), "same-as-ingredient")) {
 95           string_tree* tmp = property(return_inst.ingredients.at(i), "same-as-ingredient");
 96           if (!tmp || !tmp->atom) {
 97             raise << maybe(caller.name) << "'same-as-ingredient' metadata should take exactly one value in '" << to_original_string(return_inst) << "'\n" << end();
 98             goto finish_return_check;
 99           }
100           int ingredient_index = to_integer(tmp->value);
101           if (ingredient_index >= SIZE(caller_instruction.ingredients)) {
102             raise << maybe(caller.name) << "too few ingredients in '" << to_original_string(caller_instruction) << "'\n" << end();
103             goto finish_return_check;
104           }
105           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) {
106             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();
107           }
108         }
109       }
110       finish_return_check:;
111     }
112   }
113 }
114 
115 bool is_primitive(recipe_ordinal r) {
116   return r < MAX_PRIMITIVE_RECIPES;
117 }
118 
119 :(scenario return_type_mismatch)
120 % Hide_errors = true;
121 def main [
122   3:num <- f 2
123 ]
124 def f [
125   12:num <- next-ingredient
126   13:num <- copy 35
127   14:point <- copy 12:point/raw
128   return 14:point
129 ]
130 +error: f: return ingredient '14:point' can't be saved in '3:num'
131 
132 //: In Mu we'd like to assume that any instruction doesn't modify its
133 //: ingredients unless they're also products. The /same-as-ingredient inside
134 //: the recipe's 'return' indicates that an ingredient is intended to be
135 //: modified in place, and will help catch accidental misuse of such
136 //: 'ingredient-products' (sometimes called in-out parameters in other
137 //: languages).
138 
139 :(scenario return_same_as_ingredient)
140 % Hide_errors = true;
141 def main [
142   1:num <- copy 0
143   2:num <- test1 1:num  # call with different ingredient and product
144 ]
145 def test1 [
146   10:num <- next-ingredient
147   return 10:num/same-as-ingredient:0
148 ]
149 +error: main: '2:num <- test1 1:num' should write to '1:num' rather than '2:num'
150 
151 :(scenario return_same_as_ingredient_dummy)
152 def main [
153   1:num <- copy 0
154   _ <- test1 1:num  # call with different ingredient and product
155 ]
156 def test1 [
157   10:num <- next-ingredient
158   return 10:num/same-as-ingredient:0
159 ]
160 $error: 0
161 
162 :(code)
163 string to_string(const vector<double>& in) {
164   if (in.empty()) return "[]";
165   ostringstream out;
166   if (SIZE(in) == 1) {
167     out << no_scientific(in.at(0));
168     return out.str();
169   }
170   out << "[";
171   for (int i = 0;  i < SIZE(in);  ++i) {
172     if (i > 0) out << ", ";
173     out << no_scientific(in.at(i));
174   }
175   out << "]";
176   return out.str();
177 }