js/step2_eval.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 }
   7
   8 // read
   9 function READ(str) {
  10     return reader.read_str(str);
  11 }
  12
  13 // eval
  14 function eval_ast(ast, env) {
  15     if (types._symbol_Q(ast)) {
  16         return env[ast];
  17     } else if (types._list_Q(ast)) {
  18         return ast.map(function(a) { return EVAL(a, env); });
  19     } else if (types._vector_Q(ast)) {
  20         var v = ast.map(function(a) { return EVAL(a, env); });
  21         v.__isvector__ = true;
  22         return v;
  23     } else if (types._hash_map_Q(ast)) {
  24         var new_hm = {};
  25         for (k in ast) {
  26             new_hm[EVAL(k, env)] = EVAL(ast[k], env);
  27         }
  28         return new_hm;
  29     } else {
  30         return ast;
  31     }
  32 }
  33
  34 function _EVAL(ast, env) {
  35     //printer.println("EVAL:", printer._pr_str(ast, true));
  36     if (!types._list_Q(ast)) {
  37         return eval_ast(ast, env);
  38     }
  39
  40     // apply list
  41     var el = eval_ast(ast, env), f = el[0];
  42     return f.apply(f, el.slice(1));
  43 }
  44
  45 function EVAL(ast, env) {
  46     var result = _EVAL(ast, env);
  47     return (typeof result !== "undefined") ? result : null;
  48 }
  49
  50 // print
  51 function PRINT(exp) {
  52     return printer._pr_str(exp, true);
  53 }
  54
  55 // repl
  56 repl_env = {};
  57 var rep = function(str) { return PRINT(EVAL(READ(str), repl_env)); };
  58
  59 repl_env['+'] = function(a,b){return a+b;};
  60 repl_env['-'] = function(a,b){return a-b;};
  61 repl_env['*'] = function(a,b){return a*b;};
  62 repl_env['/'] = function(a,b){return a/b;};
  63
  64 // repl loop
  65 if (typeof require !== 'undefined' && require.main === module) {
  66     // Synchronous node.js commandline mode
  67     while (true) {
  68         var line = readline.readline("user> ");
  69         if (line === null) { break; }
  70         try {
  71             if (line) { printer.println(rep(line)); }
  72         } catch (exc) {
  73             if (exc instanceof reader.BlankException) { continue; }
  74             if (exc.stack) { printer.println(exc.stack); }
  75             else           { printer.println(exc); }
  76         }
  77     }
  78 }