https://github.com/akkartik/mu/blob/master/012transform.cc

      1 //: Phase 2: Filter loaded recipes through an extensible list of 'transforms'.
      2 //:
      3 //:   The process of running Mu code:
      4 //:     load -> transform -> run
      5 //:
      6 //: The hope is that this framework of transform tools will provide a
      7 //: deconstructed alternative to conventional compilers.
      8 //:
      9 //: We're going to have many transforms in Mu, and getting their order right
     10 //: (not the same as ordering of layers) is a well-known problem. Some tips:
     11 //:   a) Design each layer to rely on as few previous layers as possible.
     12 //:
     13 //:   b) When positioning transforms, try to find the tightest constraint in
     14 //:   each transform relative to previous layers.
     15 //:
     16 //:   c) Even so you'll periodically need to try adjusting each transform
     17 //:   relative to those in previous layers to find a better arrangement.
     18
     19 :(before "End recipe Fields")
     20 int transformed_until;
     21 :(before "End recipe Constructor")
     22 transformed_until = -1;
     23
     24 :(before "End Types")
     25 typedef void (*transform_fn)(const recipe_ordinal);
     26
     27 :(before "End Globals")
     28 vector<transform_fn> Transform;
     29
     30 :(before "End One-time Setup")
     31 initialize_transforms();
     32 :(code)
     33 void initialize_transforms() {
     34   // Begin Transforms
     35     // Begin Instruction Inserting/Deleting Transforms
     36     // End Instruction Inserting/Deleting Transforms
     37
     38     // Begin Instruction Modifying Transforms
     39     // End Instruction Modifying Transforms
     40   // End Transforms
     41
     42   // Begin Checks
     43   // End Checks
     44 }
     45
     46 void transform_all() {
     47   trace(9990, "transform") << "=== transform_all()" << end();
     48   // Begin transform_all
     49   for (int t = 0;  t < SIZE(Transform);  ++t) {
     50     for (map<recipe_ordinal, recipe>::iterator p = Recipe.begin();  p != Recipe.end();  ++p) {
     51       recipe& r = p->second;
     52       if (r.transformed_until != t-1) continue;
     53       // End Transform Checks
     54       (*Transform.at(t))(/*recipe_ordinal*/p->first);
     55       r.transformed_until = t;
     56     }
     57   }
     58   parse_int_reagents();  // do this after all other transforms have run
     59   // End transform_all
     60 }
     61
     62 //: Even though a run will involve many calls to transform_all() for tests,
     63 //: our logical model is to load all code, then transform all code, then run.
     64 //: If you load new code that should cause already-transformed recipes to
     65 //: change, that's not supported. To help detect such situations and raise
     66 //: helpful errors we track a count of the number of calls made to
     67 //: transform_all().
     68 :(before "End Globals")
     69 int Num_calls_to_transform_all = 0;
     70 :(after "void transform_all()")
     71   ++Num_calls_to_transform_all;
     72
     73 :(code)
     74 void parse_int_reagents() {
     75   trace(9991, "transform") << "--- parsing any uninitialized reagents as integers" << end();
     76   for (map<recipe_ordinal, recipe>::iterator p = Recipe.begin();  p != Recipe.end();  ++p) {
     77     recipe& r = p->second;
     78     if (r.steps.empty()) continue;
     79     for (int index = 0;  index < SIZE(r.steps);  ++index) {
     80       instruction& inst = r.steps.at(index);
     81       for (int i = 0;  i < SIZE(inst.ingredients);  ++i) {
     82         populate_value(inst.ingredients.at(i));
     83       }
     84       for (int i = 0;  i < SIZE(inst.products);  ++i) {
     85         populate_value(inst.products.at(i));
     86       }
     87     }
     88   }
     89 }
     90
     91 void populate_value(reagent& r) {
     92   if (r.initialized) return;
     93   // End Reagent-parsing Exceptions
     94   if (!is_integer(r.name)) return;
     95   r.set_value(to_integer(r.name));
     96 }
     97
     98 // helper for tests -- temporarily suppress run
     99 void transform(string form) {
    100   load(form);
    101   transform_all();
    102 }