python.2/step4_if_fn_do.py

   1 import readline
   2 from typing import Dict
   3
   4 import core
   5 import reader
   6 from env import Env
   7 from mal_types import (
   8     MalExpression,
   9     MalSymbol,
  10     MalInvalidArgumentException,
  11     MalUnknownSymbolException,
  12     MalSyntaxException,
  13 )
  14 from mal_types import (
  15     MalList,
  16     MalNil,
  17     MalBoolean,
  18     MalFunctionCompiled,
  19     MalVector,
  20     MalHash_map,
  21 )
  22
  23 repl_env = Env(None)
  24 for key in core.ns:
  25     repl_env.set(key, core.ns[key])
  26
  27
  28 def READ(x: str) -> MalExpression:
  29     return reader.read(x)
  30
  31
  32 def eval_ast(ast: MalExpression, env: Env) -> MalExpression:
  33     if isinstance(ast, MalSymbol):
  34         return env.get(ast)
  35     if isinstance(ast, MalList):
  36         return MalList([EVAL(x, env) for x in ast.native()])
  37     if isinstance(ast, MalVector):
  38         return MalVector([EVAL(x, env) for x in ast.native()])
  39     if isinstance(ast, MalHash_map):
  40         new_dict = {}  # type: Dict[str, MalExpression]
  41         for key in ast.native():
  42             new_dict[key] = EVAL(ast.native()[key], env)
  43         return MalHash_map(new_dict)
  44     return ast
  45
  46
  47 def EVAL(ast: MalExpression, env: Env) -> MalExpression:
  48     # print("EVAL: " + str(ast))
  49     if not isinstance(ast, MalList):
  50         return eval_ast(ast, env)
  51     if len(ast.native()) == 0:
  52         return ast
  53     first = str(ast.native()[0])
  54     rest = ast.native()[1:]
  55     if first == "def!":
  56         key = str(ast.native()[1])
  57         value = EVAL(ast.native()[2], env)
  58         return env.set(key, value)
  59     if first == "let*":
  60         assert len(rest) == 2
  61         let_env = Env(env)
  62         bindings = rest[0]
  63         assert isinstance(bindings, MalList) or isinstance(bindings, MalVector)
  64         bindings_list = bindings.native()
  65         assert len(bindings_list) % 2 == 0
  66         for i in range(0, len(bindings_list), 2):
  67             assert isinstance(bindings_list[i], MalSymbol)
  68             assert isinstance(bindings_list[i + 1], MalExpression)
  69             let_env.set(str(bindings_list[i]), EVAL(bindings_list[i + 1], let_env))
  70         expr = rest[1]
  71         return EVAL(expr, let_env)
  72     if first == "do":
  73         for x in range(0, len(rest) - 1):
  74             EVAL(rest[x], env)
  75         return EVAL(rest[len(rest) - 1], env)
  76     if first == "if":
  77         condition = EVAL(rest[0], env)
  78
  79         if isinstance(condition, MalNil) or (
  80             isinstance(condition, MalBoolean) and condition.native() is False
  81         ):
  82             if len(rest) >= 3:
  83                 return EVAL(rest[2], env)
  84             else:
  85                 return MalNil()
  86         else:
  87             return EVAL(rest[1], env)
  88     if first == "fn*":
  89
  90         def func_body(x):
  91             func_env = Env(outer=env, binds=rest[0].native(), exprs=x)
  92             return EVAL(rest[1], func_env)
  93
  94         return MalFunctionCompiled(func_body)
  95
  96     evaled_ast = eval_ast(ast, env)
  97     f = evaled_ast.native()[0]
  98     args = evaled_ast.native()[1:]
  99     try:
 100         return f.call(args)
 101     except AttributeError:
 102         raise MalInvalidArgumentException(f, "attribute error")
 103
 104
 105 def PRINT(x: MalExpression) -> str:
 106     return str(x)
 107
 108
 109 def rep(x: str) -> str:
 110     return PRINT(EVAL(READ(x), repl_env))
 111
 112
 113 if __name__ == "__main__":
 114     # repl loop
 115     eof: bool = False
 116     while not eof:
 117         try:
 118             line = input("user> ")
 119             readline.add_history(line)
 120             try:
 121                 print(rep(line))
 122             except MalUnknownSymbolException as e:
 123                 print("'" + e.func + "' not found")
 124             except MalSyntaxException as e:
 125                 print("ERROR: invalid syntax: " + str(e))
 126         except EOFError:
 127             eof = True