import sys, copy, types as pytypes

### python 3.0 differences
##if sys.hexversion > 0x3000000:
##    def u(x):
##        return x
##else:
##    import codecs
##    def u(x):
##        return codecs.unicode_escape_decode(x)[0]
##
##
##if sys.version_info[0] >= 3:
##    str_types = [str]
##else:
##    str_types = [str, unicode]
##
### General functions
##
##def _equal_Q(a, b):
##    ota, otb = type(a), type(b)
##    if not (ota == otb or (_sequential_Q(a) and _sequential_Q(b))):
##        return False;
##    if _symbol_Q(a):
##        return a == b
##    elif _list_Q(a) or _vector_Q(a):
##        if len(a) != len(b): return False
##        for i in range(len(a)):
##            if not _equal_Q(a[i], b[i]): return False
##        return True
##    elif _hash_map_Q(a):
##        akeys = a.keys()
##        akeys.sort()
##        bkeys = b.keys()
##        bkeys.sort()
##        if len(akeys) != len(bkeys): return False
##        for i in range(len(akeys)):
##            if akeys[i] != bkeys[i]: return False
##            if not equal_Q(a[akeys[i]], b[bkeys[i]]): return False
##        return True
##    else:
##        return a == b
##
##def _sequential_Q(seq): return _list_Q(seq) or _vector_Q(seq)
##
##def _clone(obj):
##    #if type(obj) == type(lambda x:x):
##    if type(obj) == pytypes.FunctionType:
##        if obj.__code__:
##            return pytypes.FunctionType(
##                    obj.__code__, obj.__globals__, name = obj.__name__,
##                    argdefs = obj.__defaults__, closure = obj.__closure__)
##        else:
##            return pytypes.FunctionType(
##                    obj.func_code, obj.func_globals, name = obj.func_name,
##                    argdefs = obj.func_defaults, closure = obj.func_closure)
##    else:
##        return copy.copy(obj)

def _replace(match, sub, old_str):
    new_str = u""
    idx = 0
    while idx < len(old_str):
        midx = old_str.find(match, idx)
        if midx < 0: break
        assert midx >= 0 and midx < len(old_str)
        new_str = new_str + old_str[idx:midx]
        new_str = new_str + sub
        idx = midx + len(match)
    new_str = new_str + old_str[idx:]
    return new_str

#
# Mal Types
#

### Parent type
class MalType(): pass

### Scalars
class MalNil(MalType): pass
nil = MalNil()
def _nil_Q(exp):
    assert isinstance(exp, MalType)
    return exp is nil

class MalTrue(MalType): pass
true = MalTrue()
def _true_Q(exp):
    assert isinstance(exp, MalType)
    return exp is true

class MalFalse(MalType): pass
false = MalFalse()
def _false_Q(exp):
    assert isinstance(exp, MalType)
    return exp is false

# Numbers
class MalInt(MalType):
    def __init__(self, value):
        assert isinstance(value, int)
        self.value = value
def _int_Q(exp):
    assert isinstance(exp, MalType)
    return exp.__class__ is MalInt

# String
class MalStr(MalType):
    def __init__(self, value):
        assert isinstance(value, unicode)
        self.value = value
    def __len__(self):
        return len(self.value)
def _string_Q(exp):
    assert isinstance(exp, MalType)
    return exp.__class__  is MalStr

# Symbols
class MalSym(MalType):
    def __init__(self, value):
        assert isinstance(value, unicode)
        self.value = value
def _symbol(strn):
    assert isinstance(strn, unicode)
    return MalSym(strn)
def _symbol_Q(exp):
    assert isinstance(exp, MalType)
    return exp.__class__ is MalSym

# Keywords
# A specially prefixed string
def _keyword(mstr):
    assert isinstance(mstr, MalType)
    if isinstance(mstr, MalStr):
        val = mstr.value
        if val[0] == u"\u029e": return mstr
        else:                   return MalStr(u"\u029e" + val)
    else:
        raise Exception("_keyword called on non-string")
# Create keyword from unicode string
def _keywordu(strn):
    assert isinstance(strn, unicode)
    return MalStr(u"\u029e" + strn)
def _keyword_Q(exp):
    return _string_Q(exp) and exp.value[0] == u"\u029e"

# Functions
class MalFunc(MalType):
    def __init__(self, fn):
        self.fn = fn
    def apply(self, args):
        return self.fn(args)
##def _function(Eval, Env, ast, env, params):
##    def fn(*args):
##        return Eval(ast, Env(env, params, args))
##    fn.__meta__ = None
##    fn.__ast__ = ast
##    fn.__gen_env__ = lambda args: Env(env, params, args)
##    return fn
def _function_Q(exp):
    assert isinstance(exp, MalType)
    return exp.__class__ is MalFunc

# lists
class MalList(MalType):
    def __init__(self, vals):
        assert isinstance(vals, list)
        self.values = vals
    def append(self, val):
        self.values.append(val)
    def rest(self, val):
        return MalList(self.values[1:])
    def __len__(self):
        return len(self.values)
    def __getitem__(self, i):
        assert isinstance(i, int)
        return self.values[i]

##    def __add__(self, rhs): return List(list.__add__(self, rhs))
##    def __getitem__(self, i):
##        if type(i) == slice: return List(list.__getitem__(self, i))
##        elif i >= len(self): return None
##        else:                return list.__getitem__(self, i)
##    def __getslice__(self, *a): return List(list.__getslice__(self, *a))
def _list(*vals): return MalList(list(vals))
#def _list_Q(exp): return exp.__class__ == MalList
def _list_Q(exp):
    assert isinstance(exp, MalType)
    return exp.__class__ is MalList


### vectors
##class Vector(list):
##    def __add__(self, rhs): return Vector(list.__add__(self, rhs))
##    def __getitem__(self, i):
##        if type(i) == slice: return Vector(list.__getitem__(self, i))
##        elif i >= len(self): return None
##        else:                return list.__getitem__(self, i)
##    def __getslice__(self, *a): return Vector(list.__getslice__(self, *a))
##def _vector(*vals): return Vector(vals)
##def _vector_Q(exp): return type(exp) == Vector
##
### Hash maps
##class Hash_Map(dict): pass
##def _hash_map(*key_vals):
##    hm = Hash_Map()
##    for i in range(0,len(key_vals),2): hm[key_vals[i]] = key_vals[i+1]
##    return hm
##def _hash_map_Q(exp): return type(exp) == Hash_Map
##
### atoms
##class Atom(object):
##    def __init__(self, val):
##        self.val = val
##def _atom(val): return Atom(val)
##def _atom_Q(exp):   return type(exp) == Atom