js/step5_tco.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     var core = require('./core');
   8 }
   9
  10 // read
  11 function READ(str) {
  12     return reader.read_str(str);
  13 }
  14
  15 // eval
  16 function eval_ast(ast, env) {
  17     if (types._symbol_Q(ast)) {
  18         return env.get(ast);
  19     } else if (types._list_Q(ast)) {
  20         return ast.map(function(a) { return EVAL(a, env); });
  21     } else if (types._vector_Q(ast)) {
  22         var v = ast.map(function(a) { return EVAL(a, env); });
  23         v.__isvector__ = true;
  24         return v;
  25     } else if (types._hash_map_Q(ast)) {
  26         var new_hm = {};
  27         for (k in ast) {
  28             new_hm[EVAL(k, env)] = EVAL(ast[k], env);
  29         }
  30         return new_hm;
  31     } else {
  32         return ast;
  33     }
  34 }
  35
  36 function _EVAL(ast, env) {
  37     while (true) {
  38
  39     //printer.println("EVAL:", types._pr_str(ast, true));
  40     if (!types._list_Q(ast)) {
  41         return eval_ast(ast, env);
  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].value, EVAL(a1[i+1], let_env));
  54         }
  55         return EVAL(a2, let_env);
  56     case "do":
  57         eval_ast(ast.slice(1, -1), env);
  58         ast = ast[ast.length-1];
  59         break;
  60     case "if":
  61         var cond = EVAL(a1, env);
  62         if (cond === null || cond === false) {
  63             ast = (typeof a3 !== "undefined") ? a3 : null;
  64         } else {
  65             ast = a2;
  66         }
  67         break;
  68     case "fn*":
  69         return types._function(EVAL, Env, a2, env, a1);
  70     default:
  71         var el = eval_ast(ast, env), f = el[0];
  72         if (f.__ast__) {
  73             ast = f.__ast__;
  74             env = f.__gen_env__(el.slice(1));
  75         } else {
  76             return f.apply(f, el.slice(1));
  77         }
  78     }
  79
  80     }
  81 }
  82
  83 function EVAL(ast, env) {
  84     var result = _EVAL(ast, env);
  85     return (typeof result !== "undefined") ? result : null;
  86 }
  87
  88 // print
  89 function PRINT(exp) {
  90     return printer._pr_str(exp, true);
  91 }
  92
  93 // repl
  94 var repl_env = new Env();
  95 var rep = function(str) { return PRINT(EVAL(READ(str), repl_env)); };
  96
  97 // core.js: defined using javascript
  98 for (var n in core.ns) { repl_env.set(n, core.ns[n]); }
  99 repl_env.set('eval', function(ast) { return EVAL(ast, repl_env); });
 100
 101 // core.mal: defined using the language itself
 102 rep("(def! not (fn* (a) (if a false true)))");
 103
 104 if (typeof require === 'undefined') {
 105     // Asynchronous browser mode
 106     readline.rlwrap(function(line) { return rep(line); },
 107                     function(exc) {
 108                         if (exc instanceof reader.BlankException) { return; }
 109                         if (exc.stack) { printer.println(exc.stack); }
 110                         else           { printer.println(exc); }
 111                     });
 112 } else if (require.main === module) {
 113     // Synchronous node.js commandline mode
 114     while (true) {
 115         var line = readline.readline("user> ");
 116         if (line === null) { break; }
 117         try {
 118             if (line) { printer.println(rep(line)); }
 119         } catch (exc) {
 120             if (exc instanceof reader.BlankException) { continue; }
 121             if (exc.stack) { printer.println(exc.stack); }
 122             else           { printer.println(exc); }
 123         }
 124     }
 125 } else {
 126     exports.rep = rep;
 127 }