closures.js

@@ -0,0 +1,158 @@
+/* Takes an AST and converts all of the functions into "closures"
+ * A closure is a triple of:
+ *  the bound variables in a function or let
+ *  the free variables in a function or let
+ *  a function body or let body and bound values (if it is an escaping closure only)
+ * The closure has the property that all of the free variables of the function or let
+ * are in the environment, or an exception is raised because the variable is not bound
+ * in the current environment.
+ * A free variable is simply those that are not in the list of formal parameters or bound variables if it is a let
+ *
+ * Therefore in order to call a closure one must first extract the actual function and then
+ * call the function with the environment associated with it.
+ * For the purposes of type checking it does not matter how the function gets called, the environment
+ * is only used for looking up the types of names. Formal parameters are given type variables.
+ *
+ * The first phase of closure conversion is not really closure conversion exactly.
+ * All it does is find out the free variables in scope and tie those up into a data structure with their types later.
+ * The second phase will be done to the CPS language and closures will actually lambda-lifted out potentially.
+ */
+
+var rep = require("./representation.js");
+var errors = require("./errors.js");
+var parser = require("./parse.js");
+var $ = require("./tools.js");
+var _ = require("underscore");
+
+var notEmpty = _.compose($.not, _.partial(_.equal, []));
+
+function fvs(stx) {
+  switch (stx.exprType) {
+    case "Integer":
+      return [];
+    case "Float":
+      return [];
+    case "String":
+      return [];
+    case "Function":
+      return [];
+    case "Nil":
+      return [];
+    case "Bool":
+      return [];
+    case "Let":
+      return [];
+    case "Unary":
+      return _.flatten([stx.op.ident, fvs(stx.val)]);
+    case "Definition":
+      return _.flatten(fvs(stx.val));
+    case "Application":
+      var vs = _.flatten(fvs(stx.p));
+      var f_fvs = _.flatten(fvs(stx.func));
+      return _.flatten([vs, f_fvs]);
+    case "If":
+      if (stx.elseexp) {
+        var cond_fvs = fvs(stx.condition);
+        var then_fvs = fvs(stx.thenexp);
+        var else_fvs = fvs(stx.elseexp);
+        return _.flatten([cond_fvs, then_fvs, else_fvs]);
+      }
+      else {
+        return _.flatten([fvs(stx.condition), fvs(stx.thenexp)]);
+      }
+      break;
+    case "Name":
+      return [stx.ident];
+  }
+}
+
+function annotate_fvs(stx) {
+  /* Takes a stx object that is either
+   * a lambda
+   * a let
+   * and returns a closure wrapped around that stx object
+   */
+  if (stx.exprType !== "Function" &&
+      stx.exprType !== "Let") {
+    throw errors.JInternalError(
+           ["Tried to calculate the free variables of",
+           "something that was not a function or let.\n",
+           "That something was a: " + stx.exprType +"\n"].reduce(
+                function (a,b) {
+                  return a+" "+b;
+                }, ""));
+  }
+  var variables, free_variables, bound_vars, stx_type;
+
+  switch (stx.exprType) {
+    case "Let":
+      bound_vars = stx.pairs.map(
+         function (stx) {
+           return stx.ident.ident;
+         });
+      var let_fvs = stx.pairs.map(fvs);
+      var body_fvs = fvs(stx.body);
+      variables = _.flatten(let_fvs);
+      $.extend(variables, _.flatten(body_fvs));
+      break;
+    case "Function":
+      bound_vars = [stx.p.ident,];
+      variables = fvs(stx.body);
+      break;
+  }
+  free_variables = _.difference(_.uniq(variables), bound_vars);
+  return new rep.Closure(bound_vars, free_variables, stx, []);
+}
+
+/*
+ * This traverse the tree and gathers up all of the free variables of various functions/let bindings
+ */
+function annotate_fvs_all(stx) {
+  var closure;
+  switch (stx.exprType) {
+    case "Let":
+      closure = annotate_fvs(stx);
+      closure.body.pairs = closure.body.pairs.map(annotate_fvs_all);
+      closure.body = annotate_fvs_all(closure.body.body);
+      return closure;
+    case "Function":
+      closure = annotate_fvs(stx);
+      closure.body.body = annotate_fvs_all(closure.body.body);
+      return closure;
+    case "Unary":
+      stx.val = annotate_fvs_all(stx.val);
+      return stx;
+    case "Application":
+      stx.func = annotate_fvs_all(stx.func);
+      stx.p = annotate_fvs_all(stx.p);
+      return stx;
+    case "If":
+      if (stx.elseexp) {
+        stx.condition = annotate_fvs_all(stx.condition);
+        stx.thenexp = annotate_fvs_all(stx.thenexp);
+        stx.elseexp = annotate_fvs_all(stx.elseexp);
+        return stx;
+      }
+      else {
+        stx.condition = annotate_fvs_all(stx.condition);
+        stx.thenexp = annotate_fvs_all(stx.thenexp);
+        return stx;
+      }
+      break;
+    case "Definition":
+      stx.val = annotate_fvs_all(stx.val);
+      return stx;
+    default:
+      return stx;
+  }
+}
+
+
+function test(src) {
+  var ast = parser.parse(src);
+}
+
+//console.log(test("if something then if a then if b then c else d else rtrrt else some_other_thing"));
+module.exports = {
+  annotate_fvs : annotate_fvs_all
+};

cps.js

@@ -0,0 +1,5 @@
+#! /usr/bin/node
+
+var typ = require("representation.js");
+
+

environments.js

@@ -27,23 +27,25 @@ function extend(env, values) {
 function makeEnv(name, values) {
   var env = {};
   env.name = name;
+  env.bindings = {};
   for (var i = 0; i < values.length; i++) {
-    name = values[i][0].val;
+    name = values[i][0];
     var val = values[i][1];
-    env[name] = val;
+    env.bindings[name] = val;
   }
   return env;
 }
 
 function lookup(name, env) {
-  var value = env[name];
+  var value = env.bindings[name];
   if (!value) {
-    throw errors.UnboundError(name, env.name);
+    throw errors.JUnboundError(name, env.name);
   }
   return value;
 }
 
 module.exports = {
   lookup : lookup,
-  extend : extend
+  extend : extend,
+  makeEnv : makeEnv
 };

parse.js

@@ -7,7 +7,7 @@ var tokenizer = require("./tokenize.js");
 var desugarer = require("./desugar.js");
 var pprint = require("./pprint.js");
 var error = require("./errors.js");
-
+var closure = require("./closures.js");
 var print = console.log;
 
 function sourcePos(tokens, linenum, charnum) {
@@ -808,9 +808,11 @@ function parse(tokens) {
 function parseFull(tokenized) {
   var ast = [];
   var typeBindings = {};
+  var current;
   try {
     while (tokenized.length > 0) {
-      ast.push(desugarer.desugar(parse(tokenized), typeBindings));
+      current = closure.annotate_fvs(desugarer.desugar(parse(tokenized), typeBindings));
+      ast.push(current);
     }
     return [ast, typeBindings];
   } catch (e) {
@@ -828,9 +830,10 @@ function parseFull(tokenized) {
 module.exports = { parse : function(str) {
                               return parseFull(tokenizer.tokenize(str));
                             },
-                  tokenize : tokenizer.tokenize
+                  tokenize : tokenizer.tokenize,
+                  parseFull : parseFull,
                  };
-var istr = fs.readFileSync('/dev/stdin').toString();
+//var istr = fs.readFileSync('/dev/stdin').toString();
-var testParse = parseFull(tokenizer.tokenize(istr));
+//var testParse = parseFull(tokenizer.tokenize(istr));
-console.log(testParse[1]);
+//console.log(testParse[1]);
-console.log(testParse[0].map(pprint.pprint));
+//console.log(testParse[0].map(pprint.pprint));

vm.js

@@ -0,0 +1,66 @@
+#! /usr/bin/node
+
+var typ = require("./representation.js");
+var parse = require("./parse.js");
+var tokenizer = require("./tokenize.js");
+var pprint = require("./pprint.js");
+var env = require("./environments.js");
+
+
+//var istr = fs.readFileSync('/dev/stdin').toString();
+//var istr = "if true then (+ 6 (a+a*b)) else 1";
+var istr = "def (f a) (a + b)"
+var ast = parse.parseFull(tokenizer.tokenize(istr));
+
+function apply(func, p) {
+  return func(p);
+}
+
+function evaluateAll(ast, environment) {
+  var l = ast.length;
+  var evaled = [];
+  for (var i = 0; i < l; i++) {
+    // should look for closures?
+    evaled.push(evaluate(ast[i], environment));
+  }
+  return evaled;
+}
+
+function evaluate(ast, environment) {
+  if (ast.exprType == "Application") {
+    return apply(evaluate(ast.func, environment), evaluate(ast.p, environment));
+  }
+  else if (ast.exprType === "Unary") { /* Unary function application */
+    return apply(evaluate(ast.op, environment), evaluate(ast.val, environment));
+  }
+  else if (ast.exprType === "Name") {
+    //console.log(env.lookup(ast.ident, environment));
+    return env.lookup(ast.ident, environment);
+  }
+  else if (ast.exprType === "If") {
+    if (evaluate(ast.condition, environment)) {
+      return evaluate(ast.thenexp, environment);
+    }
+    else {
+      return evaluate(ast.elseexp, environment);
+    }
+  }
+  else if (ast.exprType === "Definition") {
+    console.log(ast);
+  }
+  else {
+    return ast.val;
+  }
+}
+var testenv = env.makeEnv("toplevel",
+                      [
+                       ["+", function(a) { return function(b) { return a + b; } }],
+                       ["*", function(a) { return function(b) { return a * b; } }],
+                       ["a", 2],
+                       ["b", 3]]);
+
+var all = evaluate(ast[0][ast[0].length - 1], testenv);
+console.log(all);
+//console.log("%j", testenv);
+//console.log("%j", ast[0][ast[0].length - 1]);
+//console.log("%j", ast[0][ast[0].length - 1]);