js/step7_quote.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 is_pair(x) {
  17     return types._sequential_Q(x) && x.length > 0;
  18 }
  19
  20 function quasiquote(ast) {
  21     if (!is_pair(ast)) {
  22         return [types._symbol("quote"), ast];
  23     } else if (ast[0].value === 'unquote') {
  24         return ast[1];
  25     } else if (is_pair(ast[0]) && ast[0][0].value === 'splice-unquote') {
  26         return [types._symbol("concat"),
  27                 ast[0][1],
  28                 quasiquote(ast.slice(1))];
  29     } else {
  30         return [types._symbol("cons"),
  31                 quasiquote(ast[0]),
  32                 quasiquote(ast.slice(1))];
  33     }
  34 }
  35
  36 function eval_ast(ast, env) {
  37     if (types._symbol_Q(ast)) {
  38         return env.get(ast);
  39     } else if (types._list_Q(ast)) {
  40         return ast.map(function(a) { return EVAL(a, env); });
  41     } else if (types._vector_Q(ast)) {
  42         var v = ast.map(function(a) { return EVAL(a, env); });
  43         v.__isvector__ = true;
  44         return v;
  45     } else if (types._hash_map_Q(ast)) {
  46         var new_hm = {};
  47         for (k in ast) {
  48             new_hm[EVAL(k, env)] = EVAL(ast[k], env);
  49         }
  50         return new_hm;
  51     } else {
  52         return ast;
  53     }
  54 }
  55
  56 function _EVAL(ast, env) {
  57     while (true) {
  58
  59     //printer.println("EVAL:", printer._pr_str(ast, true));
  60     if (!types._list_Q(ast)) {
  61         return eval_ast(ast, env);
  62     }
  63
  64     // apply list
  65     var a0 = ast[0], a1 = ast[1], a2 = ast[2], a3 = ast[3];
  66     switch (a0.value) {
  67     case "def!":
  68         var res = EVAL(a2, env);
  69         return env.set(a1, res);
  70     case "let*":
  71         var let_env = new Env(env);
  72         for (var i=0; i < a1.length; i+=2) {
  73             let_env.set(a1[i].value, EVAL(a1[i+1], let_env));
  74         }
  75         ast = a2;
  76         env = let_env;
  77         break;
  78     case "quote":
  79         return a1;
  80     case "quasiquote":
  81         ast = quasiquote(a1);
  82         break;
  83     case "do":
  84         eval_ast(ast.slice(1, -1), env);
  85         ast = ast[ast.length-1];
  86         break;
  87     case "if":
  88         var cond = EVAL(a1, env);
  89         if (cond === null || cond === false) {
  90             ast = (typeof a3 !== "undefined") ? a3 : null;
  91         } else {
  92             ast = a2;
  93         }
  94         break;
  95     case "fn*":
  96         return types._function(EVAL, Env, a2, env, a1);
  97     default:
  98         var el = eval_ast(ast, env), f = el[0];
  99         if (f.__ast__) {
 100             ast = f.__ast__;
 101             env = f.__gen_env__(el.slice(1));
 102         } else {
 103             return f.apply(f, el.slice(1));
 104         }
 105     }
 106
 107     }
 108 }
 109
 110 function EVAL(ast, env) {
 111     var result = _EVAL(ast, env);
 112     return (typeof result !== "undefined") ? result : null;
 113 }
 114
 115 // print
 116 function PRINT(exp) {
 117     return printer._pr_str(exp, true);
 118 }
 119
 120 // repl
 121 var repl_env = new Env();
 122 var rep = function(str) { return PRINT(EVAL(READ(str), repl_env)); };
 123
 124 // core.js: defined using javascript
 125 for (var n in core.ns) { repl_env.set(n, core.ns[n]); }
 126 repl_env.set('eval', function(ast) { return EVAL(ast, repl_env); });
 127 repl_env.set('*ARGV*', []);
 128
 129 // core.mal: defined using the language itself
 130 rep("(def! not (fn* (a) (if a false true)))");
 131 rep("(def! load-file (fn* (f) (eval (read-string (str \"(do \" (slurp f) \")\")))))");
 132
 133 if (typeof process !== 'undefined' && process.argv.length > 2) {
 134     repl_env.set('*ARGV*', process.argv.slice(3));
 135     rep('(load-file "' + process.argv[2] + '")');
 136     process.exit(0);
 137 }
 138
 139 // repl loop
 140 if (typeof require !== 'undefined' && require.main === module) {
 141     // Synchronous node.js commandline mode
 142     while (true) {
 143         var line = readline.readline("user> ");
 144         if (line === null) { break; }
 145         try {
 146             if (line) { printer.println(rep(line)); }
 147         } catch (exc) {
 148             if (exc instanceof reader.BlankException) { continue; }
 149             if (exc.stack) { printer.println(exc.stack); }
 150             else           { printer.println(exc); }
 151         }
 152     }
 153 }