rpython/step8_macros.py

   1 import sys, traceback
   2 import mal_readline
   3 import mal_types as types
   4 from mal_types import (MalSym, MalInt, MalStr,
   5                        nil, true, false, _symbol, _keywordu,
   6                        MalList, _list, MalVector, MalHashMap, MalFunc)
   7 import reader, printer
   8 from env import Env
   9 import core
  10
  11 # read
  12 def READ(str):
  13     return reader.read_str(str)
  14
  15 # eval
  16 def is_pair(x):
  17     return types._sequential_Q(x) and len(x) > 0
  18
  19 def quasiquote(ast):
  20     if not is_pair(ast):
  21         return _list(_symbol(u"quote"), ast)
  22     else:
  23         a0 = ast[0]
  24         if isinstance(a0, MalSym):
  25             if a0.value == u'unquote':
  26                 return ast[1]
  27         if is_pair(a0) and isinstance(a0[0], MalSym):
  28             a00 = a0[0]
  29             if (isinstance(a00, MalSym) and
  30                 a00.value == u'splice-unquote'):
  31                 return _list(_symbol(u"concat"),
  32                              a0[1],
  33                              quasiquote(ast.rest()))
  34     return _list(_symbol(u"cons"),
  35                 quasiquote(a0),
  36                 quasiquote(ast.rest()))
  37
  38 def is_macro_call(ast, env):
  39     if types._list_Q(ast):
  40         a0 = ast[0]
  41         if isinstance(a0, MalSym):
  42             if not env.find(a0) is None:
  43                 return env.get(a0).ismacro
  44     return False
  45
  46 def macroexpand(ast, env):
  47     while is_macro_call(ast, env):
  48         assert isinstance(ast[0], MalSym)
  49         mac = env.get(ast[0])
  50         ast = macroexpand(mac.apply(ast.rest()), env)
  51     return ast
  52
  53 def eval_ast(ast, env):
  54     if types._symbol_Q(ast):
  55         assert isinstance(ast, MalSym)
  56         return env.get(ast)
  57     elif types._list_Q(ast):
  58         res = []
  59         for a in ast.values:
  60             res.append(EVAL(a, env))
  61         return MalList(res)
  62     elif types._vector_Q(ast):
  63         res = []
  64         for a in ast.values:
  65             res.append(EVAL(a, env))
  66         return MalVector(res)
  67     elif types._hash_map_Q(ast):
  68         new_dct = {}
  69         for k in ast.dct.keys():
  70             new_dct[k] = EVAL(ast.dct[k], env)
  71         return MalHashMap(new_dct)
  72     else:
  73         return ast  # primitive value, return unchanged
  74
  75 def EVAL(ast, env):
  76     while True:
  77         #print("EVAL %s" % printer._pr_str(ast))
  78         if not types._list_Q(ast):
  79             return eval_ast(ast, env)
  80         if len(ast) == 0: return ast
  81
  82         # apply list
  83         ast = macroexpand(ast, env)
  84         if not types._list_Q(ast):
  85             return eval_ast(ast, env)
  86         if len(ast) == 0: return ast
  87         a0 = ast[0]
  88         if isinstance(a0, MalSym):
  89             a0sym = a0.value
  90         else:
  91             a0sym = u"__<*fn*>__"
  92
  93         if u"def!" == a0sym:
  94             a1, a2 = ast[1], ast[2]
  95             res = EVAL(a2, env)
  96             return env.set(a1, res)
  97         elif u"let*" == a0sym:
  98             a1, a2 = ast[1], ast[2]
  99             let_env = Env(env)
 100             for i in range(0, len(a1), 2):
 101                 let_env.set(a1[i], EVAL(a1[i+1], let_env))
 102             ast = a2
 103             env = let_env # Continue loop (TCO)
 104         elif u"quote" == a0sym:
 105             return ast[1]
 106         elif u"quasiquote" == a0sym:
 107             ast = quasiquote(ast[1]) # Continue loop (TCO)
 108         elif u"defmacro!" == a0sym:
 109             func = EVAL(ast[2], env)
 110             func.ismacro = True
 111             return env.set(ast[1], func)
 112         elif u"macroexpand" == a0sym:
 113             return macroexpand(ast[1], env)
 114         elif u"do" == a0sym:
 115             if len(ast) == 0:
 116                 return nil
 117             elif len(ast) > 1:
 118                 eval_ast(ast.slice2(1, len(ast)-1), env)
 119             ast = ast[-1] # Continue loop (TCO)
 120         elif u"if" == a0sym:
 121             a1, a2 = ast[1], ast[2]
 122             cond = EVAL(a1, env)
 123             if cond is nil or cond is false:
 124                 if len(ast) > 3: ast = ast[3] # Continue loop (TCO)
 125                 else:            return nil
 126             else:
 127                 ast = a2 # Continue loop (TCO)
 128         elif u"fn*" == a0sym:
 129             a1, a2 = ast[1], ast[2]
 130             return MalFunc(None, a2, env, a1, EVAL)
 131         else:
 132             el = eval_ast(ast, env)
 133             f = el.values[0]
 134             if isinstance(f, MalFunc):
 135                 if f.ast:
 136                     ast = f.ast
 137                     env = f.gen_env(el.rest()) # Continue loop (TCO)
 138                 else:
 139                     return f.apply(el.rest())
 140             else:
 141                 raise Exception("%s is not callable" % f)
 142
 143 # print
 144 def PRINT(exp):
 145     return printer._pr_str(exp)
 146
 147 # repl
 148 class MalEval(MalFunc):
 149     def apply(self, args):
 150         return self.EvalFunc(args[0], self.env)
 151
 152 def entry_point(argv):
 153     repl_env = Env()
 154     def REP(str, env):
 155         return PRINT(EVAL(READ(str), env))
 156
 157     # core.py: defined using python
 158     for k, v in core.ns.items():
 159         repl_env.set(_symbol(unicode(k)), MalFunc(v))
 160     repl_env.set(types._symbol(u'eval'),
 161                  MalEval(None, env=repl_env, EvalFunc=EVAL))
 162     mal_args = []
 163     if len(argv) >= 3:
 164         for a in argv[2:]: mal_args.append(MalStr(unicode(a)))
 165     repl_env.set(_symbol(u'*ARGV*'), MalList(mal_args))
 166
 167     # core.mal: defined using the language itself
 168     REP("(def! not (fn* (a) (if a false true)))", repl_env)
 169     REP("(def! load-file (fn* (f) (eval (read-string (str \"(do \" (slurp f) \")\")))))", repl_env)
 170     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)))))))", repl_env)
 171     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))))))))", repl_env)
 172
 173     if len(argv) >= 2:
 174         REP('(load-file "' + argv[1] + '")', repl_env)
 175         return 0
 176
 177     while True:
 178         try:
 179             line = mal_readline.readline("user> ")
 180             if line == "": continue
 181             print(REP(line, repl_env))
 182         except EOFError as e:
 183             break
 184         except reader.Blank:
 185             continue
 186         except types.MalException as e:
 187             print(u"Error: %s" % printer._pr_str(e.object, False))
 188         except Exception as e:
 189             print("Error: %s" % e)
 190             #print("".join(traceback.format_exception(*sys.exc_info())))
 191     return 0
 192
 193 # _____ Define and setup target ___
 194 def target(*args):
 195     return entry_point
 196
 197 # Just run entry_point if not RPython compilation
 198 import sys
 199 if not sys.argv[0].endswith('rpython'):
 200     entry_point(sys.argv)