88 lines
2.3 KiB
JavaScript
88 lines
2.3 KiB
JavaScript
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// Credit to http://m1el.github.io/smallest-lambda-eval/
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function Eval(prog, env) {
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if (typeof prog === 'string') {
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// lookup a variable
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return env[prog];
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} else if (prog[0] === '$') {
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// constructing a new lambda
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return (arg) => Eval(prog[2], { ...env, [prog[1]]: arg });
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} else {
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// function application
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return Eval(prog[0], env)(Eval(prog[1], env));
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}
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}
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function FromChurch(f) {
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var i = 0;
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f(function (x) {
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i++;
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return x;
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})(function (x) {
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return x;
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})(undefined);
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}
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function ToChurch(i) {
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return function (a) {
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return function (b) {
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var c = b;
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for (let j = 0; j < i; j++)c = a(c);
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return c
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}
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}
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}
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function FromArray(x) {
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return x([])((a) => (v) => [...a, v])
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}
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function ToArray(x) {
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return function (n) {
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return function (s) {
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var o = n;
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for (var i of x) {
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o = s(o)(i);
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}
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return o
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}
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}
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}
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function FromString(x) {
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return String.fromCodePoint(...FromArray(x).map(FromChurch))
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}
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function ToString(s){
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return toArray([...s].map(x => x.codePointAt(0)).map(FromChurch))
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}
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var opcodes = {
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0: 'io_ref_new',
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1: 'io_ref_read',
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2: 'io_ref_write',
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}
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function RunIO(prog) {
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return prog(function(x){
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return x;
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})(function (ty) {
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return function (pay) {
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return function (cont) {
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var then = function(x){
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return RunIO(cont(x))
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}
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switch (opcodes[FromChurch(ty)]) {
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case 'io_ref_new':
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var x = Math.random().toString();
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RunIO["io_ref/" + x] = pay;
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return then(ToString(x));
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case 'io_ref_read':
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return then(RunIO["io_ref/" + FromString(pay)])
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case 'io_ref_write':
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return pay(function(a){
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return function(b){
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RunIO["io_ref/" + FromString(a)] = b;
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return then(b);
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}
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})
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}
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}
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}
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})
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}
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RunIO(Eval([["$","val",["$","p",["$","i",["p","val"]]]],["$","+",["$","0","0"]]],{}))
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