python/stepA_more.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 is_macro_call(ast, env):
  32     return (types._list_Q(ast) and
  33             types._symbol_Q(ast[0]) and
  34             env.find(ast[0]) and
  35             hasattr(env.get(ast[0]), '_ismacro_'))
  36
  37 def macroexpand(ast, env):
  38     while is_macro_call(ast, env):
  39         mac = env.get(ast[0])
  40         ast = macroexpand(mac(*ast[1:]), env)
  41     return ast
  42
  43 def eval_ast(ast, env):
  44     if types._symbol_Q(ast):
  45         return env.get(ast)
  46     elif types._list_Q(ast):
  47         return types._list(*map(lambda a: EVAL(a, env), ast))
  48     elif types._vector_Q(ast):
  49         return types._vector(*map(lambda a: EVAL(a, env), ast))
  50     elif types._hash_map_Q(ast):
  51         keyvals = []
  52         for k in ast.keys():
  53             keyvals.append(EVAL(k, env))
  54             keyvals.append(EVAL(ast[k], env))
  55         return types._hash_map(*keyvals)
  56     else:
  57         return ast  # primitive value, return unchanged
  58
  59 def EVAL(ast, env):
  60     while True:
  61         #print("EVAL %s" % ast)
  62         if not types._list_Q(ast):
  63             return eval_ast(ast, env)
  64
  65         # apply list
  66         ast = macroexpand(ast, env)
  67         if not types._list_Q(ast): return ast
  68         if len(ast) == 0: return ast
  69         a0 = ast[0]
  70
  71         if "def!" == a0:
  72             a1, a2 = ast[1], ast[2]
  73             res = EVAL(a2, env)
  74             return env.set(a1, res)
  75         elif "let*" == a0:
  76             a1, a2 = ast[1], ast[2]
  77             let_env = Env(env)
  78             for i in range(0, len(a1), 2):
  79                 let_env.set(a1[i], EVAL(a1[i+1], let_env))
  80             return EVAL(a2, let_env)
  81         elif "quote" == a0:
  82             return ast[1]
  83         elif "quasiquote" == a0:
  84             return EVAL(quasiquote(ast[1]), env)
  85         elif 'defmacro!' == a0:
  86             func = EVAL(ast[2], env)
  87             func._ismacro_ = True
  88             return env.set(ast[1], func)
  89         elif 'macroexpand' == a0:
  90             return macroexpand(ast[1], env)
  91         elif "py!*" == a0:
  92             if sys.version_info[0] >= 3:
  93                 exec(compile(ast[1], '', 'single'), globals())
  94             else:
  95                 exec(compile(ast[1], '', 'single') in globals())
  96             return None
  97         elif "py*" == a0:
  98             return eval(ast[1])
  99         elif "." == a0:
 100             el = eval_ast(ast[2:], env)
 101             f = eval(ast[1])
 102             return f(*el)
 103         elif "try*" == a0:
 104             a1, a2 = ast[1], ast[2]
 105             if a2[0] == "catch*":
 106                 try:
 107                     return EVAL(a1, env);
 108                 except Exception as exc:
 109                     exc = exc.args[0]
 110                     catch_env = Env(env, [a2[1]], [exc])
 111                     return EVAL(a2[2], catch_env)
 112             else:
 113                 return EVAL(a1, env);
 114         elif "do" == a0:
 115             eval_ast(ast[1:-1], env)
 116             ast = ast[-1]
 117             # Continue loop (TCO)
 118         elif "if" == a0:
 119             a1, a2 = ast[1], ast[2]
 120             cond = EVAL(a1, env)
 121             if cond is None or cond is False:
 122                 if len(ast) > 3: ast = ast[3]
 123                 else:            ast = None
 124             else:
 125                 ast = a2
 126             # Continue loop (TCO)
 127         elif "fn*" == a0:
 128             a1, a2 = ast[1], ast[2]
 129             return types._function(EVAL, Env, a2, env, a1)
 130         else:
 131             el = eval_ast(ast, env)
 132             f = el[0]
 133             if hasattr(f, '__ast__'):
 134                 ast = f.__ast__
 135                 env = f.__gen_env__(el[1:])
 136             else:
 137                 return f(*el[1:])
 138
 139 # print
 140 def PRINT(exp):
 141     return printer._pr_str(exp)
 142
 143 # repl
 144 repl_env = Env()
 145 def REP(str):
 146     return PRINT(EVAL(READ(str), repl_env))
 147
 148 # core.py: defined using python
 149 for k, v in core.ns.items(): repl_env.set(k, v)
 150 repl_env.set('eval', lambda ast: EVAL(ast, repl_env))
 151
 152 # core.mal: defined using the language itself
 153 REP("(def! not (fn* (a) (if a false true)))")
 154 REP("(def! load-file (fn* (f) (eval (read-string (str \"(do \" (slurp f) \")\")))))")
 155 REP("(defmacro! cond (fn* (& xs) (if (> (count xs) 0) (list 'if (first xs) (if (> (count xs) 1) (nth xs 1) (throw \"odd number of forms to cond\")) (cons 'cond (rest (rest xs)))))))")
 156 REP("(defmacro! or (fn* (& xs) (if (empty? xs) nil (if (= 1 (count xs)) (first xs) `(let* (or_FIXME ~(first xs)) (if or_FIXME or_FIXME (or ~@(rest xs))))))))")
 157
 158 if len(sys.argv) >= 2:
 159     REP('(load-file "' + sys.argv[1] + '")')
 160 else:
 161     while True:
 162         try:
 163             line = mal_readline.readline("user> ")
 164             if line == None: break
 165             if line == "": continue
 166             print(REP(line))
 167         except reader.Blank: continue
 168         except Exception as e:
 169             print("".join(traceback.format_exception(*sys.exc_info())))