122 lines
2.6 KiB
JavaScript
122 lines
2.6 KiB
JavaScript
// Type representations:
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//
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// number are numbers
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//
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// cons pairs are [first, rest]
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//
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// function closures are Closures
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// primitive procedures are regular functions.
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var TopEnvironment = function() {
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this.globalBindings = {
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'=': function(argl) {
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return argl[0] === argl[1][0];
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},
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'+': function(argl) {
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return argl[0] + argl[1][0];
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},
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'*': function(argl) {
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return argl[0] * argl[1][0];
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},
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'-': function(argl) {
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return argl[0] - argl[1][0];
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},
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'/': function(argl) {
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return argl[0] / argl[1][0];
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}
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};
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this.valss = [];
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};
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var ExtendedEnvironment = function(parent, vs) {
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var vals = [];
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while(vs) {
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vals.push(vs[0]);
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vs = vs[1];
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}
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this.valss = parent.valss.slice();
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this.valss.unshift(vals);
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this.globalBindings = parent.globalBindings;
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};
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// A closure consists of its free variables as well as a label
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// into its text segment.
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var Closure = function(env, label) {
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this.env = env;
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this.label = label;
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};
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// adaptToJs: closure -> (array (X -> void) -> void)
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// Converts closures to functions that can be called from the
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// JavaScript toplevel.
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Closure.prototype.adaptToJs = function() {
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var that = this;
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return function(args, k) {
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var oldEnv = MACHINE.env;
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var oldCont = MACHINE.cont;
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var oldProc = MACHINE.proc;
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var oldArgl = MACHINE.argl;
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var oldVal = MACHINE.val;
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trampoline(
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function() {
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var proc = that;
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MACHINE.proc = proc;
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MACHINE.argl = undefined;
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for(var i = args.length - 1; i >= 0; i--) {
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MACHINE.argl = [args[i], MACHINE.argl];
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}
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MACHINE.cont = function() {
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var result = MACHINE.val;
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MACHINE.env = oldEnv;
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MACHINE.cont = oldCont;
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MACHINE.proc = oldProc;
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MACHINE.argl = oldArgl;
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MACHINE.val = oldVal;
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k(result);
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};
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proc.label();
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},
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function() {
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});
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}
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};
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var MACHINE={callsBeforeTrampoline: 100,
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env: new TopEnvironment(),
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proc:undefined,
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argl:undefined,
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val:undefined,
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cont:undefined,
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stack: []};
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// harness: (->) (->) -> void
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var trampoline = function(initialJump, k) {
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var thunk = initialJump;
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MACHINE.callsBeforeTrampoline = 100;
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while(thunk) {
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try {
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thunk();
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break;
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} catch (e) {
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if (typeof(e) === 'function') {
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thunk = e;
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MACHINE.callsBeforeTrampoline = 100;
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} else {
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throw e;
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}
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}
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}
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k();
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};
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