python.2/step3_env.py

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