2306 - recipe headers

Once a student has gotten used to recipes and ingredients using the
staged 'next-ingredient' approach there's no reason to avoid
conventional function headers. As an added bonus we can now:

a) check that all 'reply' instructions in a recipe are consistent
b) deduce what to reply without needing to say so everytime
c) start thinking about type parameters for recipes (generic functions!)

10 files changed, 132 insertions, 16 deletions

diff --git a/010vm.cc b/010vm.cc
index 47a2d01c..08da15a3 100644
--- a/010vm.cc
+++ b/010vm.cc
@@ -38,6 +38,7 @@ struct instruction {
   // End instruction Fields
   instruction();
   void clear();
+  bool is_clear();
   string to_string() const;
 };
 
@@ -222,6 +223,7 @@ instruction::instruction() :is_label(false), operation(IDLE) {
   // End instruction Constructor
 }
 void instruction::clear() { is_label=false; label.clear(); operation=IDLE; ingredients.clear(); products.clear(); }
+bool instruction::is_clear() { return !is_label && operation == IDLE; }
 
 // Reagents have the form <name>:<type>:<type>:.../<property>/<property>/...
 reagent::reagent(string s) :original_string(s), value(0), initialized(false), type(NULL) {
diff --git a/011load.cc b/011load.cc
index 7c7bded0..3e1766f9 100644
--- a/011load.cc
+++ b/011load.cc
@@ -52,27 +52,26 @@ long long int slurp_recipe(istream& in) {
       raise << "redefining recipe " << Recipe[Recipe_ordinal[recipe_name]].name << "\n" << end();
     Recipe.erase(Recipe_ordinal[recipe_name]);
   }
-  // todo: save user-defined recipes to mu's memory
-  Recipe[Recipe_ordinal[recipe_name]] = slurp_body(in);
-  Recipe[Recipe_ordinal[recipe_name]].name = recipe_name;
+  recipe& result = Recipe[Recipe_ordinal[recipe_name]];
+  result.name = recipe_name;
+  slurp_body(in, result);
   // track added recipes because we may need to undo them in tests; see below
   recently_added_recipes.push_back(Recipe_ordinal[recipe_name]);
   return Recipe_ordinal[recipe_name];
 }
 
-recipe slurp_body(istream& in) {
+void slurp_body(istream& in, recipe& result) {
   in >> std::noskipws;
-  recipe result;
   skip_whitespace(in);
   if (in.get() != '[')
     raise_error << "recipe body must begin with '['\n" << end();
   skip_whitespace_and_comments(in);
   instruction curr;
   while (next_instruction(in, &curr)) {
-    // End Rewrite Instruction(curr)
-    result.steps.push_back(curr);
+    // End Rewrite Instruction(curr, recipe result)
+    if (!curr.is_clear())
+      result.steps.push_back(curr);
   }
-  return result;
 }
 
 bool next_instruction(istream& in, instruction* curr) {
diff --git a/021check_instruction.cc b/021check_instruction.cc
index afece2bf..6df7a2d1 100644
--- a/021check_instruction.cc
+++ b/021check_instruction.cc
@@ -88,7 +88,7 @@ bool types_match(reagent lhs, reagent rhs) {
 // (trees perform the same check recursively on each subtree)
 bool types_match(type_tree* lhs, type_tree* rhs) {
   if (!lhs) return true;
-  if (rhs->value == 0) {
+  if (!rhs || rhs->value == 0) {
     if (lhs->value == Type_ordinal["array"]) return false;
     if (lhs->value == Type_ordinal["address"]) return false;
     return size_of(rhs) == size_of(lhs);
diff --git a/036call_reply.cc b/036call_reply.cc
index 8a4653ca..4f96a38b 100644
--- a/036call_reply.cc
+++ b/036call_reply.cc
@@ -165,7 +165,7 @@ recipe test1 [
 ]
 +mem: storing 34 in location 1
 
-:(before "End Rewrite Instruction(curr)")
+:(before "End Rewrite Instruction(curr, recipe result)")
 // rewrite `reply-if a, b, c, ...` to
 //   ```
 //   jump-unless a, 1:offset
diff --git a/044space.cc b/044space.cc
index ed074336..56b494d5 100644
--- a/044space.cc
+++ b/044space.cc
@@ -117,7 +117,7 @@ if (x.name == "number-of-locals")
 :(before "End is_special_name Cases")
 if (s == "number-of-locals") return true;
 
-:(before "End Rewrite Instruction(curr)")
+:(before "End Rewrite Instruction(curr, recipe result)")
 // rewrite `new-default-space` to
 //   `default-space:address:array:location <- new location:type, number-of-locals:literal`
 // where N is Name[recipe][""]
@@ -162,7 +162,7 @@ try_reclaim_locals();
 
 //: now 'local-scope' is identical to 'new-default-space' except that we'll
 //: reclaim the default-space when the routine exits
-:(before "End Rewrite Instruction(curr)")
+:(before "End Rewrite Instruction(curr, recipe result)")
 if (curr.name == "local-scope") {
   rewrite_default_space_instruction(curr);
 }
diff --git a/052tangle.cc b/052tangle.cc
index 2c393a31..7995e501 100644
--- a/052tangle.cc
+++ b/052tangle.cc
@@ -35,7 +35,8 @@ Fragments_used.clear();
 :(before "End Command Handlers")
 else if (command == "before") {
   string label = next_word(in);
-  recipe tmp = slurp_body(in);
+  recipe tmp;
+  slurp_body(in, tmp);
   if (is_waypoint(label))
     Before_fragments[label].steps.insert(Before_fragments[label].steps.end(), tmp.steps.begin(), tmp.steps.end());
   else
@@ -43,7 +44,8 @@ else if (command == "before") {
 }
 else if (command == "after") {
   string label = next_word(in);
-  recipe tmp = slurp_body(in);
+  recipe tmp;
+  slurp_body(in, tmp);
   if (is_waypoint(label))
     After_fragments[label].steps.insert(After_fragments[label].steps.begin(), tmp.steps.begin(), tmp.steps.end());
   else
diff --git a/056recipe_header.cc b/056recipe_header.cc
new file mode 100644
index 00000000..37855908
--- /dev/null
+++ b/056recipe_header.cc
@@ -0,0 +1,111 @@
+//: Advanced notation for the common/easy case where a recipe takes some fixed
+//: number of ingredients and yields some fixed number of products.
+
+:(scenario recipe_with_header)
+recipe main [
+  1:number/raw <- add2 3, 5
+]
+recipe add2 x:number, y:number -> z:number [
+  local-scope
+  load-ingredients
+  z:number <- add x, y
+  reply z
+]
++mem: storing 8 in location 1
+
+//: When loading recipes save any header.
+
+:(before "End recipe Fields")
+vector<reagent> ingredients;
+vector<reagent> products;
+
+:(before "slurp_body(in, result);" following "long long int slurp_recipe(istream& in)")
+skip_whitespace(in);
+if (in.peek() != '[') {
+  load_recipe_header(in, result);
+}
+
+:(code)
+void load_recipe_header(istream& in, recipe& result) {
+  while (in.peek() != '[') {
+    string s = next_word(in);
+    if (s == "->") break;
+    result.ingredients.push_back(reagent(s));
+    skip_whitespace(in);
+  }
+  while (in.peek() != '[') {
+    string s = next_word(in);
+    result.products.push_back(reagent(s));
+    skip_whitespace(in);
+  }
+}
+
+//: Now rewrite 'load-ingredients' to instructions to create all reagents in
+//: the header.
+
+:(before "End Rewrite Instruction(curr, recipe result)")
+if (curr.name == "load-ingredients") {
+  curr.clear();
+  for (long long int i = 0; i < SIZE(result.ingredients); ++i) {
+    curr.operation = Recipe_ordinal["next-ingredient"];
+    curr.name = "next-ingredient";
+    curr.products.push_back(result.ingredients.at(i));
+    result.steps.push_back(curr);
+    curr.clear();
+  }
+}
+
+:(scenarios transform)
+:(scenario recipe_headers_are_checked)
+% Hide_warnings = true;
+recipe add2 x:number, y:number -> z:number [
+  local-scope
+  load-ingredients
+  z:address:number <- copy 0/raw
+  reply z
+]
++warn: add2: replied with the wrong type at 'reply z'
+
+:(before "End One-time Setup")
+  Transform.push_back(check_header_products);
+
+:(code)
+void check_header_products(const recipe_ordinal r) {
+  const recipe& rr = Recipe[r];
+  if (rr.products.empty()) return;
+  for (long long int i = 0; i < SIZE(rr.steps); ++i) {
+    const instruction& inst = rr.steps.at(i);
+    if (inst.operation != REPLY) continue;
+    if (SIZE(rr.products) != SIZE(inst.ingredients)) {
+      raise << maybe(rr.name) << "tried to reply the wrong number of products in '" << inst.to_string() << "'\n" << end();
+    }
+    for (long long int i = 0; i < SIZE(rr.products); ++i) {
+      if (!types_match(rr.products.at(i), inst.ingredients.at(i))) {
+        raise << maybe(rr.name) << "replied with the wrong type at '" << inst.to_string() << "'\n" << end();
+      }
+    }
+  }
+}
+
+//: One final convenience: no need to say what to return if the information is
+//: in the header.
+
+:(scenarios run)
+:(scenario reply_based_on_header)
+recipe main [
+  1:number/raw <- add2 3, 5
+]
+recipe add2 x:number, y:number -> z:number [
+  local-scope
+  load-ingredients
+  z:number <- add x, y
+  reply
+]
++mem: storing 8 in location 1
+
+:(before "End Rewrite Instruction(curr, recipe result)")
+if (curr.name == "reply" && curr.ingredients.empty()) {
+  for (long long int i = 0; i < SIZE(result.products); ++i) {
+    curr.ingredients.push_back(result.products.at(i));
+  }
+}
diff --git a/072scenario_screen.cc b/072scenario_screen.cc
index f9536bc5..11151eac 100644
--- a/072scenario_screen.cc
+++ b/072scenario_screen.cc
@@ -137,7 +137,7 @@ const long long int SCREEN = Next_predefined_global_for_scenarios++;
 :(before "End Special Scenario Variable Names(r)")
 Name[r]["screen"] = SCREEN;
 
-:(before "End Rewrite Instruction(curr)")
+:(before "End Rewrite Instruction(curr, recipe result)")
 // rewrite `assume-screen width, height` to
 // `screen:address:screen <- new-fake-screen width, height`
 if (curr.name == "assume-screen") {
diff --git a/075scenario_console.cc b/075scenario_console.cc
index f8e3e1a1..47cb5f29 100644
--- a/075scenario_console.cc
+++ b/075scenario_console.cc
@@ -50,7 +50,8 @@ case ASSUME_CONSOLE: {
 case ASSUME_CONSOLE: {
   // create a temporary recipe just for parsing; it won't contain valid instructions
   istringstream in("[" + current_instruction().ingredients.at(0).name + "]");
-  recipe r = slurp_body(in);
+  recipe r;
+  slurp_body(in, r);
   long long int num_events = count_events(r);
   // initialize the events like in new-fake-console
   long long int size = num_events*size_of_event() + /*space for length*/1;
diff --git a/mu.vim b/mu.vim
index 72255940..bb77b50d 100644
--- a/mu.vim
+++ b/mu.vim
@@ -62,6 +62,7 @@ syntax match muGlobal %[^ ]\+:global/\?[^ ,]*% | highlight link muGlobal Special
 syntax keyword muControl reply reply-if reply-unless jump jump-if jump-unless loop loop-if loop-unless break break-if break-unless current-continuation continue-from create-delimited-continuation reply-delimited-continuation | highlight muControl ctermfg=3
 " common keywords
 syntax keyword muRecipe recipe recipe! before after | highlight muRecipe ctermfg=208
+syntax match muRecipe " -> "
 syntax keyword muScenario scenario | highlight muScenario ctermfg=34
 syntax keyword muData container exclusive-container | highlight muData ctermfg=226