python/step6_file.py

   1 import sys, traceback
   2 import mal_readline
   3 import mal_types as types
   4 import reader, printer
   5 from env import Env
   6 import core
   7
   8 # read
   9 def READ(str):
  10     return reader.read_str(str)
  11
  12 # eval
  13 def eval_ast(ast, env):
  14     if types._symbol_Q(ast):
  15         return env.get(ast)
  16     elif types._list_Q(ast):
  17         return types._list(*map(lambda a: EVAL(a, env), ast))
  18     elif types._vector_Q(ast):
  19         return types._vector(*map(lambda a: EVAL(a, env), ast))
  20     elif types._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 types._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" % printer._pr_str(ast))
  32         if not types._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             ast = a2
  49             env = let_env
  50             # Continue loop (TCO)
  51         elif "do" == a0:
  52             eval_ast(ast[1:-1], env)
  53             ast = ast[-1]
  54             # Continue loop (TCO)
  55         elif "if" == a0:
  56             a1, a2 = ast[1], ast[2]
  57             cond = EVAL(a1, env)
  58             if cond is None or cond is False:
  59                 if len(ast) > 3: ast = ast[3]
  60                 else:            ast = None
  61             else:
  62                 ast = a2
  63             # Continue loop (TCO)
  64         elif "fn*" == a0:
  65             a1, a2 = ast[1], ast[2]
  66             return types._function(EVAL, Env, a2, env, a1)
  67         else:
  68             el = eval_ast(ast, env)
  69             f = el[0]
  70             if hasattr(f, '__ast__'):
  71                 ast = f.__ast__
  72                 env = f.__gen_env__(el[1:])
  73             else:
  74                 return f(*el[1:])
  75
  76 # print
  77 def PRINT(exp):
  78     return printer._pr_str(exp)
  79
  80 # repl
  81 repl_env = Env()
  82 def REP(str):
  83     return PRINT(EVAL(READ(str), repl_env))
  84
  85 # core.py: defined using python
  86 for k, v in core.ns.items(): repl_env.set(types._symbol(k), v)
  87 repl_env.set(types._symbol('eval'), lambda ast: EVAL(ast, repl_env))
  88 repl_env.set(types._symbol('*ARGV*'), types._list(*sys.argv[2:]))
  89
  90 # core.mal: defined using the language itself
  91 REP("(def! not (fn* (a) (if a false true)))")
  92 REP("(def! load-file (fn* (f) (eval (read-string (str \"(do \" (slurp f) \")\")))))")
  93
  94 if len(sys.argv) >= 2:
  95     REP('(load-file "' + sys.argv[1] + '")')
  96     sys.exit(0)
  97
  98 # repl loop
  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 reader.Blank: continue
 106     except Exception as e:
 107         print("".join(traceback.format_exception(*sys.exc_info())))