js/step3_env.js

   1 if (typeof module !== 'undefined') {
   2     var types = require('./types');
   3     var readline = require('./node_readline');
   4     var reader = require('./reader');
   5     var printer = require('./printer');
   6     var Env = require('./env').Env;
   7 }
   8
   9 // read
  10 function READ(str) {
  11     return reader.read_str(str);
  12 }
  13
  14 // eval
  15 function eval_ast(ast, env) {
  16     if (types._symbol_Q(ast)) {
  17         return env.get(ast);
  18     } else if (types._list_Q(ast)) {
  19         return ast.map(function(a) { return EVAL(a, env); });
  20     } else if (types._vector_Q(ast)) {
  21         var v = ast.map(function(a) { return EVAL(a, env); });
  22         v.__isvector__ = true;
  23         return v;
  24     } else if (types._hash_map_Q(ast)) {
  25         var new_hm = {};
  26         for (k in ast) {
  27             new_hm[EVAL(k, env)] = EVAL(ast[k], env);
  28         }
  29         return new_hm;
  30     } else {
  31         return ast;
  32     }
  33 }
  34
  35 function _EVAL(ast, env) {
  36     //printer.println("EVAL:", printer._pr_str(ast, true));
  37     if (!types._list_Q(ast)) {
  38         return eval_ast(ast, env);
  39     }
  40     if (ast.length === 0) {
  41         return ast;
  42     }
  43
  44     // apply list
  45     var a0 = ast[0], a1 = ast[1], a2 = ast[2], a3 = ast[3];
  46     switch (a0.value) {
  47     case "def!":
  48         var res = EVAL(a2, env);
  49         return env.set(a1, res);
  50     case "let*":
  51         var let_env = new Env(env);
  52         for (var i=0; i < a1.length; i+=2) {
  53             let_env.set(a1[i], EVAL(a1[i+1], let_env));
  54         }
  55         return EVAL(a2, let_env);
  56     default:
  57         var el = eval_ast(ast, env), f = el[0];
  58         return f.apply(f, el.slice(1));
  59     }
  60 }
  61
  62 function EVAL(ast, env) {
  63     var result = _EVAL(ast, env);
  64     return (typeof result !== "undefined") ? result : null;
  65 }
  66
  67 // print
  68 function PRINT(exp) {
  69     return printer._pr_str(exp, true);
  70 }
  71
  72 // repl
  73 var repl_env = new Env();
  74 var rep = function(str) { return PRINT(EVAL(READ(str), repl_env)); };
  75
  76 repl_env.set(types._symbol('+'), function(a,b){return a+b;});
  77 repl_env.set(types._symbol('-'), function(a,b){return a-b;});
  78 repl_env.set(types._symbol('*'), function(a,b){return a*b;});
  79 repl_env.set(types._symbol('/'), function(a,b){return a/b;});
  80
  81 // repl loop
  82 if (typeof require !== 'undefined' && require.main === module) {
  83     // Synchronous node.js commandline mode
  84     while (true) {
  85         var line = readline.readline("user> ");
  86         if (line === null) { break; }
  87         try {
  88             if (line) { printer.println(rep(line)); }
  89         } catch (exc) {
  90             if (exc instanceof reader.BlankException) { continue }
  91             if (exc instanceof Error) { console.warn(exc.stack) }
  92             else { console.warn("Error: " + printer._pr_str(exc, true)) }
  93         }
  94     }
  95 }