impls/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" % printer._pr_str(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             ast = a2
  67             env = let_env
  68             # Continue loop (TCO)
  69         elif "quote" == a0:
  70             return ast[1]
  71         elif "quasiquote" == a0:
  72             ast = quasiquote(ast[1]);
  73             # Continue loop (TCO)
  74         elif "do" == a0:
  75             eval_ast(ast[1:-1], env)
  76             ast = ast[-1]
  77             # Continue loop (TCO)
  78         elif "if" == a0:
  79             a1, a2 = ast[1], ast[2]
  80             cond = EVAL(a1, env)
  81             if cond is None or cond is False:
  82                 if len(ast) > 3: ast = ast[3]
  83                 else:            ast = None
  84             else:
  85                 ast = a2
  86             # Continue loop (TCO)
  87         elif "fn*" == a0:
  88             a1, a2 = ast[1], ast[2]
  89             return types._function(EVAL, Env, a2, env, a1)
  90         else:
  91             el = eval_ast(ast, env)
  92             f = el[0]
  93             if hasattr(f, '__ast__'):
  94                 ast = f.__ast__
  95                 env = f.__gen_env__(el[1:])
  96             else:
  97                 return f(*el[1:])
  98
  99 # print
 100 def PRINT(exp):
 101     return printer._pr_str(exp)
 102
 103 # repl
 104 repl_env = Env()
 105 def REP(str):
 106     return PRINT(EVAL(READ(str), repl_env))
 107
 108 # core.py: defined using python
 109 for k, v in core.ns.items(): repl_env.set(types._symbol(k), v)
 110 repl_env.set(types._symbol('eval'), lambda ast: EVAL(ast, repl_env))
 111 repl_env.set(types._symbol('*ARGV*'), types._list(*sys.argv[2:]))
 112
 113 # core.mal: 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) \"\nnil)\")))))")
 116
 117 if len(sys.argv) >= 2:
 118     REP('(load-file "' + sys.argv[1] + '")')
 119     sys.exit(0)
 120
 121 # repl loop
 122 while True:
 123     try:
 124         line = mal_readline.readline("user> ")
 125         if line == None: break
 126         if line == "": continue
 127         print(REP(line))
 128     except reader.Blank: continue
 129     except Exception as e:
 130         print("".join(traceback.format_exception(*sys.exc_info())))