php/step9_try.php

   1 <?php
   2
   3 require_once 'readline.php';
   4 require_once 'types.php';
   5 require_once 'reader.php';
   6 require_once 'printer.php';
   7 require_once 'env.php';
   8 require_once 'core.php';
   9
  10 // read
  11 function READ($str) {
  12     return read_str($str);
  13 }
  14
  15 // eval
  16 function is_pair($x) {
  17     return _sequential_Q($x) and count($x) > 0;
  18 }
  19
  20 function quasiquote($ast) {
  21     if (!is_pair($ast)) {
  22         return _list(_symbol("quote"), $ast);
  23     } elseif (_symbol_Q($ast[0]) && $ast[0]->value === 'unquote') {
  24         return $ast[1];
  25     } elseif (is_pair($ast[0]) && _symbol_Q($ast[0][0]) &&
  26               $ast[0][0]->value === 'splice-unquote') {
  27         return _list(_symbol("concat"), $ast[0][1],
  28                      quasiquote($ast->slice(1)));
  29     } else {
  30         return _list(_symbol("cons"), quasiquote($ast[0]),
  31                      quasiquote($ast->slice(1)));
  32     }
  33 }
  34
  35 function is_macro_call($ast, $env) {
  36     return is_pair($ast) &&
  37            _symbol_Q($ast[0]) &&
  38            $env->find($ast[0]) &&
  39            $env->get($ast[0])->ismacro;
  40 }
  41
  42 function macroexpand($ast, $env) {
  43     while (is_macro_call($ast, $env)) {
  44         $mac = $env->get($ast[0]);
  45         $args = array_slice($ast->getArrayCopy(),1);
  46         $ast = $mac->apply($args);
  47     }
  48     return $ast;
  49 }
  50
  51 function eval_ast($ast, $env) {
  52     if (_symbol_Q($ast)) {
  53         return $env->get($ast);
  54     } elseif (_sequential_Q($ast)) {
  55         if (_list_Q($ast)) {
  56             $el = _list();
  57         } else {
  58             $el = _vector();
  59         }
  60         foreach ($ast as $a) { $el[] = MAL_EVAL($a, $env); }
  61         return $el;
  62     } elseif (_hash_map_Q($ast)) {
  63         $new_hm = _hash_map();
  64         foreach (array_keys($ast->getArrayCopy()) as $key) {
  65             $new_hm[$key] = MAL_EVAL($ast[$key], $env);
  66         }
  67         return $new_hm;
  68     } else {
  69         return $ast;
  70     }
  71 }
  72
  73 function MAL_EVAL($ast, $env) {
  74     while (true) {
  75
  76     #echo "MAL_EVAL: " . _pr_str($ast) . "\n";
  77     if (!_list_Q($ast)) {
  78         return eval_ast($ast, $env);
  79     }
  80
  81     // apply list
  82     $ast = macroexpand($ast, $env);
  83     if (!_list_Q($ast)) {
  84         return eval_ast($ast, $env);
  85     }
  86     if ($ast->count() === 0) {
  87         return $ast;
  88     }
  89
  90     $a0 = $ast[0];
  91     $a0v = (_symbol_Q($a0) ? $a0->value : $a0);
  92     switch ($a0v) {
  93     case "def!":
  94         $res = MAL_EVAL($ast[2], $env);
  95         return $env->set($ast[1], $res);
  96     case "let*":
  97         $a1 = $ast[1];
  98         $let_env = new Env($env);
  99         for ($i=0; $i < count($a1); $i+=2) {
 100             $let_env->set($a1[$i], MAL_EVAL($a1[$i+1], $let_env));
 101         }
 102         $ast = $ast[2];
 103         $env = $let_env;
 104         break; // Continue loop (TCO)
 105     case "quote":
 106         return $ast[1];
 107     case "quasiquote":
 108         $ast = quasiquote($ast[1]);
 109         break; // Continue loop (TCO)
 110     case "defmacro!":
 111         $func = MAL_EVAL($ast[2], $env);
 112         $func->ismacro = true;
 113         return $env->set($ast[1], $func);
 114     case "macroexpand":
 115         return macroexpand($ast[1], $env);
 116     case "try*":
 117         $a1 = $ast[1];
 118         $a2 = $ast[2];
 119         if ($a2[0]->value === "catch*") {
 120             try {
 121                 return MAL_EVAL($a1, $env);
 122             } catch (_Error $e) {
 123                 $catch_env = new Env($env, array($a2[1]),
 124                                             array($e->obj));
 125                 return MAL_EVAL($a2[2], $catch_env);
 126             } catch (Exception $e) {
 127                 $catch_env = new Env($env, array($a2[1]),
 128                                             array($e->getMessage()));
 129                 return MAL_EVAL($a2[2], $catch_env);
 130             }
 131         } else {
 132             return MAL_EVAL($a1, $env);
 133         }
 134     case "do":
 135         eval_ast($ast->slice(1, -1), $env);
 136         $ast = $ast[count($ast)-1];
 137         break; // Continue loop (TCO)
 138     case "if":
 139         $cond = MAL_EVAL($ast[1], $env);
 140         if ($cond === NULL || $cond === false) {
 141             if (count($ast) === 4) { $ast = $ast[3]; }
 142             else                   { $ast = NULL; }
 143         } else {
 144             $ast = $ast[2];
 145         }
 146         break; // Continue loop (TCO)
 147     case "fn*":
 148         return _function('MAL_EVAL', 'native',
 149                          $ast[2], $env, $ast[1]);
 150     default:
 151         $el = eval_ast($ast, $env);
 152         $f = $el[0];
 153         $args = array_slice($el->getArrayCopy(), 1);
 154         if ($f->type === 'native') {
 155             $ast = $f->ast;
 156             $env = $f->gen_env($args);
 157             // Continue loop (TCO)
 158         } else {
 159             return $f->apply($args);
 160         }
 161     }
 162
 163     }
 164 }
 165
 166 // print
 167 function MAL_PRINT($exp) {
 168     return _pr_str($exp, True);
 169 }
 170
 171 // repl
 172 $repl_env = new Env(NULL);
 173 function rep($str) {
 174     global $repl_env;
 175     return MAL_PRINT(MAL_EVAL(READ($str), $repl_env));
 176 }
 177
 178 // core.php: defined using PHP
 179 foreach ($core_ns as $k=>$v) {
 180     $repl_env->set(_symbol($k), _function($v));
 181 }
 182 $repl_env->set(_symbol('eval'), _function(function($ast) {
 183     global $repl_env; return MAL_EVAL($ast, $repl_env);
 184 }));
 185 $_argv = _list();
 186 for ($i=2; $i < count($argv); $i++) {
 187     $_argv->append($argv[$i]);
 188 }
 189 $repl_env->set(_symbol('*ARGV*'), $_argv);
 190
 191 // core.mal: defined using the language itself
 192 rep("(def! not (fn* (a) (if a false true)))");
 193 rep("(def! load-file (fn* (f) (eval (read-string (str \"(do \" (slurp f) \")\")))))");
 194 rep("(defmacro! cond (fn* (& xs) (if (> (count xs) 0) (list 'if (first xs) (if (> (count xs) 1) (nth xs 1) (throw \"odd number of forms to cond\")) (cons 'cond (rest (rest xs)))))))");
 195 rep("(defmacro! or (fn* (& xs) (if (empty? xs) nil (if (= 1 (count xs)) (first xs) `(let* (or_FIXME ~(first xs)) (if or_FIXME or_FIXME (or ~@(rest xs))))))))");
 196
 197 if (count($argv) > 1) {
 198     rep('(load-file "' . $argv[1] . '")');
 199     exit(0);
 200 }
 201
 202 // repl loop
 203 do {
 204     try {
 205         $line = mal_readline("user> ");
 206         if ($line === NULL) { break; }
 207         if ($line !== "") {
 208             print(rep($line) . "\n");
 209         }
 210     } catch (BlankException $e) {
 211         continue;
 212     } catch (_Error $e) {
 213         echo "Error: " . _pr_str($e->obj, True) . "\n";
 214     } catch (Exception $e) {
 215         echo "Error: " . $e->getMessage() . "\n";
 216         echo $e->getTraceAsString() . "\n";
 217     }
 218 } while (true);
 219
 220 ?>