js/step4_if_fn_do.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     //printer.println("EVAL:", printer._pr_str(ast, true));
  38     if (!types._list_Q(ast)) {
  39         return eval_ast(ast, env);
  40     }
  41
  42     // apply list
  43     var a0 = ast[0], a1 = ast[1], a2 = ast[2], a3 = ast[3];
  44     switch (a0.value) {
  45     case "def!":
  46         var res = EVAL(a2, env);
  47         return env.set(a1, res);
  48     case "let*":
  49         var let_env = new Env(env);
  50         for (var i=0; i < a1.length; i+=2) {
  51             let_env.set(a1[i].value, EVAL(a1[i+1], let_env));
  52         }
  53         return EVAL(a2, let_env);
  54     case "do":
  55         var el = eval_ast(ast.slice(1), env);
  56         return el[el.length-1];
  57     case "if":
  58         var cond = EVAL(a1, env);
  59         if (cond === null || cond === false) {
  60             return typeof a3 !== "undefined" ? EVAL(a3, env) : null;
  61         } else {
  62             return EVAL(a2, env);
  63         }
  64     case "fn*":
  65         return function() {
  66             return EVAL(a2, new Env(env, a1, arguments));
  67         };
  68     default:
  69         var el = eval_ast(ast, env), f = el[0];
  70         return f.apply(f, el.slice(1));
  71     }
  72 }
  73
  74 function EVAL(ast, env) {
  75     var result = _EVAL(ast, env);
  76     return (typeof result !== "undefined") ? result : null;
  77 }
  78
  79 // print
  80 function PRINT(exp) {
  81     return printer._pr_str(exp, true);
  82 }
  83
  84 // repl
  85 var repl_env = new Env();
  86 var rep = function(str) { return PRINT(EVAL(READ(str), repl_env)); };
  87
  88 // core.js: defined using javascript
  89 for (var n in core.ns) { repl_env.set(n, core.ns[n]); }
  90
  91 // core.mal: defined using the language itself
  92 rep("(def! not (fn* (a) (if a false true)))");
  93
  94 // repl loop
  95 if (typeof require !== 'undefined' && require.main === module) {
  96     // Synchronous node.js commandline mode
  97     while (true) {
  98         var line = readline.readline("user> ");
  99         if (line === null) { break; }
 100         try {
 101             if (line) { printer.println(rep(line)); }
 102         } catch (exc) {
 103             if (exc instanceof reader.BlankException) { continue; }
 104             if (exc.stack) { printer.println(exc.stack); }
 105             else           { printer.println(exc); }
 106         }
 107     }
 108 }