python/step6_file.py

   1 import sys, traceback
   2 import mal_readline
   3 from mal_types import (pr_str, sequential_Q, symbol_Q, coll_Q, list_Q,
   4                        vector_Q, hash_map_Q, new_symbol, new_function,
   5                        new_list, new_vector, new_hash_map, Env, types_ns)
   6 from reader import (read_str, Blank)
   7
   8 # read
   9 def READ(str):
  10     return read_str(str)
  11
  12 # eval
  13 def eval_ast(ast, env):
  14     if symbol_Q(ast):
  15         return env.get(ast)
  16     elif list_Q(ast):
  17         return new_list(*map(lambda a: EVAL(a, env), ast))
  18     elif vector_Q(ast):
  19         return new_vector(*map(lambda a: EVAL(a, env), ast))
  20     elif hash_map_Q(ast):
  21         keyvals = []
  22         for k in ast.keys():
  23             keyvals.append(EVAL(k, env))
  24             keyvals.append(EVAL(ast[k], env))
  25         return new_hash_map(*keyvals)
  26     else:
  27         return ast  # primitive value, return unchanged
  28
  29 def EVAL(ast, env):
  30     while True:
  31         #print("EVAL %s" % ast)
  32         if not list_Q(ast):
  33             return eval_ast(ast, env)
  34
  35         # apply list
  36         if len(ast) == 0: return ast
  37         a0 = ast[0]
  38
  39         if "def!" == a0:
  40             a1, a2 = ast[1], ast[2]
  41             res = EVAL(a2, env)
  42             return env.set(a1, res)
  43         elif "let*" == a0:
  44             a1, a2 = ast[1], ast[2]
  45             let_env = Env(env)
  46             for i in range(0, len(a1), 2):
  47                 let_env.set(a1[i], EVAL(a1[i+1], let_env))
  48             return EVAL(a2, let_env)
  49         elif "do" == a0:
  50             eval_ast(ast[1:-1], env)
  51             ast = ast[-1]
  52             # Continue loop (TCO)
  53         elif "if" == a0:
  54             a1, a2 = ast[1], ast[2]
  55             cond = EVAL(a1, env)
  56             if cond is None or cond is False:
  57                 if len(ast) > 3: ast = ast[3]
  58                 else:            ast = None
  59             else:
  60                 ast = a2
  61             # Continue loop (TCO)
  62         elif "fn*" == a0:
  63             a1, a2 = ast[1], ast[2]
  64             return new_function(EVAL, a2, env, a1)
  65         else:
  66             el = eval_ast(ast, env)
  67             f = el[0]
  68             if hasattr(f, '__meta__') and f.__meta__.has_key("exp"):
  69                 m = f.__meta__
  70                 ast = m['exp']
  71                 env = Env(m['env'], m['params'], el[1:])
  72             else:
  73                 return f(*el[1:])
  74
  75 # print
  76 def PRINT(exp):
  77     return pr_str(exp)
  78
  79 # repl
  80 repl_env = Env()
  81 def REP(str):
  82     return PRINT(EVAL(READ(str), repl_env))
  83 def _ref(k,v): repl_env.set(k, v)
  84
  85 # Import types functions
  86 for name, val in types_ns.items(): _ref(name, val)
  87
  88 _ref('read-string', read_str)
  89 _ref('eval', lambda ast: EVAL(ast, repl_env))
  90 _ref('slurp', lambda file: open(file).read())
  91
  92 # Defined using the language itself
  93 REP("(def! not (fn* (a) (if a false true)))")
  94 REP("(def! load-file (fn* (f) (eval (read-string (str \"(do \" (slurp f) \")\")))))")
  95
  96 if len(sys.argv) >= 2:
  97     REP('(load-file "' + sys.argv[1] + '")')
  98 else:
  99     while True:
 100         try:
 101             line = mal_readline.readline("user> ")
 102             if line == None: break
 103             if line == "": continue
 104             print(REP(line))
 105         except Blank: continue
 106         except Exception as e:
 107             print "".join(traceback.format_exception(*sys.exc_info()))