lisp.js/misc/env_test.js

A tiny lisp interpreter

var _ = require('underscore');
var Env = function(params, args, outer) {
    var dict = {};
    var that = this;
    var outer = outer;
    _.forEach(params, function(ele, index) {
        dict[ele] = args[index];
    });
    this.find = function(name) {
        if (dict[name]) return that;
        return outer.find(name);
    };
    this.update = function(new_dict) {
        _.extend(dict, new_dict);
    };
    this.get = function(name) {
        if (dict[name]) return dict[name];
    };
    this.set = function(name, val) {
        dict[name] = val;
    };
};

var add_globals = function(env) {
    env.update({
        "+": function() {
            var args = Array.prototype.slice(arguments);
            return _.reduce(args, function(x, y) {
                return x+y;
            });
        },
        "-": function() {
            var args = Array.prototype.slice(arguments);
            return _.reduce(args, function(x, y) {
                return x-y;
            });
        },
        "*": function() {
            var args = Array.prototype.slice(arguments);
            return _.reduce(args, function(x, y) {
                return x*y;
            });
        },
        "/": function() {
            var args = Array.prototype.slice(arguments);
            return _.reduce(args, function(x, y) {
                return x/y;
            });
        },
        "not": function(val) { return !val; },
        ">":   function(x, y) { return x > y; },
        "<":   function(x, y) { return x < y; },
        ">=":  function(x, y) { return x >= y; },
        "<=":  function(x, y) { return x <= y; },
        "=":   function(x, y) { return x === y; },
        "equal?": function(x, y) { return x === y; },
        "eq?": function(x, y) { return x == y; },
        "length": function(x) { return x.length },
        "cons": function(x, y) { return [x, y]; },
        "car": function(x) { return x[0]; },
        "cdr": function(x) { return x.prototype.slice(1); },
        "append": function(x, y) { x.push(y); return x; },
        "list": function() { return Array.prototype.slice(arguments); },
        "list?": function(x) { return isa(x, "list"); },
        "null?": function(x) { return _.isEmpty(x); },
        "symbol?": function(x) { return isa(x, "Symbol"); }
    });
    return env;
};

var global_env = add_globals(new Env());

var env = new Env();
env.update({a: 3, b: 4});
console.log(env.find("a"));
console.log(env.find("a").get("a"));
var env2 = new Env(["c"], [5], env);
console.log(env2.find("a"));
console.log(env2.find("a").get("a"));


console.log(global_env.get("+")(3, 4));