python/step3_env.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
   7 # read
   8 def READ(str):
   9     return reader.read_str(str)
  10
  11 # eval
  12 def eval_ast(ast, env):
  13     if types._symbol_Q(ast):
  14         return env.get(ast)
  15     elif types._list_Q(ast):
  16         return types._list(*map(lambda a: EVAL(a, env), ast))
  17     elif types._vector_Q(ast):
  18         return types._vector(*map(lambda a: EVAL(a, env), ast))
  19     elif types._hash_map_Q(ast):
  20         keyvals = []
  21         for k in ast.keys():
  22             keyvals.append(EVAL(k, env))
  23             keyvals.append(EVAL(ast[k], env))
  24         return types._hash_map(*keyvals)
  25     else:
  26         return ast  # primitive value, return unchanged
  27
  28 def EVAL(ast, env):
  29         #print("EVAL %s" % ast)
  30         if not types._list_Q(ast):
  31             return eval_ast(ast, env)
  32
  33         # apply list
  34         if len(ast) == 0: return ast
  35         a0 = ast[0]
  36
  37         if "def!" == a0:
  38             a1, a2 = ast[1], ast[2]
  39             res = EVAL(a2, env)
  40             return env.set(a1, res)
  41         elif "let*" == a0:
  42             a1, a2 = ast[1], ast[2]
  43             let_env = Env(env)
  44             for i in range(0, len(a1), 2):
  45                 let_env.set(a1[i], EVAL(a1[i+1], let_env))
  46             return EVAL(a2, let_env)
  47         else:
  48             el = eval_ast(ast, env)
  49             f = el[0]
  50             return f(*el[1:])
  51
  52 # print
  53 def PRINT(exp):
  54     return printer._pr_str(exp)
  55
  56 # repl
  57 repl_env = Env()
  58 def REP(str):
  59     return PRINT(EVAL(READ(str), repl_env))
  60
  61 repl_env.set('+', lambda a,b: a+b)
  62 repl_env.set('-', lambda a,b: a-b)
  63 repl_env.set('*', lambda a,b: a*b)
  64 repl_env.set('/', lambda a,b: int(a/b))
  65
  66 while True:
  67     try:
  68         line = mal_readline.readline("user> ")
  69         if line == None: break
  70         if line == "": continue
  71         print(REP(line))
  72     except reader.Blank: continue
  73     except Exception as e:
  74         print("".join(traceback.format_exception(*sys.exc_info())))