python/step7_quote.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 is_pair(x):
  14     return types._sequential_Q(x) and len(x) > 0
  15
  16 def quasiquote(ast):
  17     if not is_pair(ast):
  18         return types._list(types._symbol("quote"),
  19                            ast)
  20     elif ast[0] == 'unquote':
  21         return ast[1]
  22     elif is_pair(ast[0]) and ast[0][0] == 'splice-unquote':
  23         return types._list(types._symbol("concat"),
  24                            ast[0][1],
  25                            quasiquote(ast[1:]))
  26     else:
  27         return types._list(types._symbol("cons"),
  28                            quasiquote(ast[0]),
  29                            quasiquote(ast[1:]))
  30
  31 def eval_ast(ast, env):
  32     if types._symbol_Q(ast):
  33         return env.get(ast)
  34     elif types._list_Q(ast):
  35         return types._list(*map(lambda a: EVAL(a, env), ast))
  36     elif types._vector_Q(ast):
  37         return types._vector(*map(lambda a: EVAL(a, env), ast))
  38     elif types._hash_map_Q(ast):
  39         keyvals = []
  40         for k in ast.keys():
  41             keyvals.append(EVAL(k, env))
  42             keyvals.append(EVAL(ast[k], env))
  43         return types._hash_map(*keyvals)
  44     else:
  45         return ast  # primitive value, return unchanged
  46
  47 def EVAL(ast, env):
  48     while True:
  49         #print("EVAL %s" % ast)
  50         if not types._list_Q(ast):
  51             return eval_ast(ast, env)
  52
  53         # apply list
  54         if len(ast) == 0: return ast
  55         a0 = ast[0]
  56
  57         if "def!" == a0:
  58             a1, a2 = ast[1], ast[2]
  59             res = EVAL(a2, env)
  60             return env.set(a1, res)
  61         elif "let*" == a0:
  62             a1, a2 = ast[1], ast[2]
  63             let_env = Env(env)
  64             for i in range(0, len(a1), 2):
  65                 let_env.set(a1[i], EVAL(a1[i+1], let_env))
  66             return EVAL(a2, let_env)
  67         elif "quote" == a0:
  68             return ast[1]
  69         elif "quasiquote" == a0:
  70             return EVAL(quasiquote(ast[1]), env)
  71         elif "do" == a0:
  72             eval_ast(ast[1:-1], env)
  73             ast = ast[-1]
  74             # Continue loop (TCO)
  75         elif "if" == a0:
  76             a1, a2 = ast[1], ast[2]
  77             cond = EVAL(a1, env)
  78             if cond is None or cond is False:
  79                 if len(ast) > 3: ast = ast[3]
  80                 else:            ast = None
  81             else:
  82                 ast = a2
  83             # Continue loop (TCO)
  84         elif "fn*" == a0:
  85             a1, a2 = ast[1], ast[2]
  86             return types._function(EVAL, Env, a2, env, a1)
  87         else:
  88             el = eval_ast(ast, env)
  89             f = el[0]
  90             if hasattr(f, '__ast__'):
  91                 ast = f.__ast__
  92                 env = f.__gen_env__(el[1:])
  93             else:
  94                 return f(*el[1:])
  95
  96 # print
  97 def PRINT(exp):
  98     return printer._pr_str(exp)
  99
 100 # repl
 101 repl_env = Env()
 102 def REP(str):
 103     return PRINT(EVAL(READ(str), repl_env))
 104 def _ref(k,v): repl_env.set(k, v)
 105
 106 # Import types functions
 107 for name, val in core.ns.items(): _ref(name, val)
 108
 109 _ref('read-string', reader.read_str)
 110 _ref('eval', lambda ast: EVAL(ast, repl_env))
 111 _ref('slurp', lambda file: open(file).read())
 112
 113 # Defined using the language itself
 114 REP("(def! not (fn* (a) (if a false true)))")
 115 REP("(def! load-file (fn* (f) (eval (read-string (str \"(do \" (slurp f) \")\")))))")
 116
 117 if len(sys.argv) >= 2:
 118     REP('(load-file "' + sys.argv[1] + '")')
 119 else:
 120     while True:
 121         try:
 122             line = mal_readline.readline("user> ")
 123             if line == None: break
 124             if line == "": continue
 125             print(REP(line))
 126         except reader.Blank: continue
 127         except Exception as e:
 128             print "".join(traceback.format_exception(*sys.exc_info()))