diff options
Diffstat (limited to 'Lib/decimal.py')
| -rw-r--r-- | Lib/decimal.py | 525 |
1 files changed, 219 insertions, 306 deletions
diff --git a/Lib/decimal.py b/Lib/decimal.py index faf9bf71d9..7842cb2507 100644 --- a/Lib/decimal.py +++ b/Lib/decimal.py @@ -214,10 +214,10 @@ class InvalidOperation(DecimalException): def handle(self, context, *args): if args: if args[0] == 1: # sNaN, must drop 's' but keep diagnostics - ans = Decimal((args[1]._sign, args[1]._int, 'n')) + ans = _dec_from_triple(args[1]._sign, args[1]._int, 'n', True) return ans._fix_nan(context) elif args[0] == 2: - return Decimal( (args[1], args[2], 'n') ) + return _dec_from_triple(args[1], args[2], 'n', True) return NaN @@ -350,13 +350,13 @@ class Overflow(Inexact, Rounded): if sign == 0: if context.rounding == ROUND_CEILING: return Infsign[sign] - return Decimal((sign, (9,)*context.prec, - context.Emax-context.prec+1)) + return _dec_from_triple(sign, '9'*context.prec, + context.Emax-context.prec+1) if sign == 1: if context.rounding == ROUND_FLOOR: return Infsign[sign] - return Decimal( (sign, (9,)*context.prec, - context.Emax-context.prec+1)) + return _dec_from_triple(sign, '9'*context.prec, + context.Emax-context.prec+1) class Underflow(Inexact, Rounded, Subnormal): @@ -531,13 +531,21 @@ class Decimal(object): Decimal("314") """ + # Note that the coefficient, self._int, is actually stored as + # a string rather than as a tuple of digits. This speeds up + # the "digits to integer" and "integer to digits" conversions + # that are used in almost every arithmetic operation on + # Decimals. This is an internal detail: the as_tuple function + # and the Decimal constructor still deal with tuples of + # digits. + self = object.__new__(cls) self._is_special = False # From an internal working value if isinstance(value, _WorkRep): self._sign = value.sign - self._int = tuple(map(int, str(value.int))) + self._int = str(value.int) self._exp = int(value.exp) return self @@ -556,7 +564,7 @@ class Decimal(object): else: self._sign = 1 self._exp = 0 - self._int = tuple(map(int, str(abs(value)))) + self._int = str(abs(value)) return self # tuple/list conversion (possibly from as_tuple()) @@ -573,7 +581,7 @@ class Decimal(object): self._sign = value[0] if value[2] == 'F': # infinity: value[1] is ignored - self._int = (0,) + self._int = '0' self._exp = value[2] self._is_special = True else: @@ -590,12 +598,12 @@ class Decimal(object): "0 through 9.") if value[2] in ('n', 'N'): # NaN: digits form the diagnostic - self._int = tuple(digits) + self._int = ''.join(map(str, digits)) self._exp = value[2] self._is_special = True elif isinstance(value[2], int): # finite number: digits give the coefficient - self._int = tuple(digits or [0]) + self._int = ''.join(map(str, digits or [0])) self._exp = value[2] self._is_special = False else: @@ -608,38 +616,46 @@ class Decimal(object): raise TypeError("Cannot convert float to Decimal. " + "First convert the float to a string") - # Other argument types may require the context during interpretation - if context is None: - context = getcontext() - # From a string # REs insist on real strings, so we can too. if isinstance(value, str): - if _isinfinity(value): - self._exp = 'F' - self._int = (0,) - self._is_special = True - if _isinfinity(value) == 1: - self._sign = 0 + m = _parser(value) + if m is None: + if context is None: + context = getcontext() + return context._raise_error(ConversionSyntax, + "Invalid literal for Decimal: %r" % value) + + if m.group('sign') == "-": + self._sign = 1 + else: + self._sign = 0 + intpart = m.group('int') + if intpart is not None: + # finite number + fracpart = m.group('frac') + exp = int(m.group('exp') or '0') + if fracpart is not None: + self._int = (intpart+fracpart).lstrip('0') or '0' + self._exp = exp - len(fracpart) else: - self._sign = 1 - return self - if _isnan(value): - sig, sign, diag = _isnan(value) - self._is_special = True - if sig == 1: - self._exp = 'n' # qNaN - else: # sig == 2 - self._exp = 'N' # sNaN - self._sign = sign - self._int = tuple(map(int, diag)) # Diagnostic info - return self - try: - self._sign, self._int, self._exp = _string2exact(value) - except ValueError: + self._int = intpart.lstrip('0') or '0' + self._exp = exp + self._is_special = False + else: + diag = m.group('diag') + if diag is not None: + # NaN + self._int = diag.lstrip('0') + if m.group('signal'): + self._exp = 'N' + else: + self._exp = 'n' + else: + # infinity + self._int = '0' + self._exp = 'F' self._is_special = True - return context._raise_error(ConversionSyntax, - "Invalid literal for Decimal: %r" % value) return self raise TypeError("Cannot convert %r to Decimal" % value) @@ -709,7 +725,7 @@ class Decimal(object): NaNs and infinities are considered nonzero. """ - return self._is_special or self._int[0] != 0 + return self._is_special or self._int != '0' def __cmp__(self, other): other = _convert_other(other) @@ -743,8 +759,8 @@ class Decimal(object): self_adjusted = self.adjusted() other_adjusted = other.adjusted() if self_adjusted == other_adjusted: - self_padded = self._int + (0,)*(self._exp - other._exp) - other_padded = other._int + (0,)*(other._exp - self._exp) + self_padded = self._int + '0'*(self._exp - other._exp) + other_padded = other._int + '0'*(other._exp - self._exp) return cmp(self_padded, other_padded) * (-1)**self._sign elif self_adjusted > other_adjusted: return (-1)**self._sign @@ -827,7 +843,7 @@ class Decimal(object): To show the internals exactly as they are. """ - return (self._sign, self._int, self._exp) + return (self._sign, tuple(map(int, self._int)), self._exp) def __repr__(self): """Represents the number as an instance of Decimal.""" @@ -843,10 +859,10 @@ class Decimal(object): if self._is_special: if self._isnan(): minus = '-'*self._sign - if self._int == (0,): + if self._int == '0': info = '' else: - info = ''.join(map(str, self._int)) + info = self._int if self._isnan() == 2: return minus + 'sNaN' + info return minus + 'NaN' + info @@ -857,7 +873,7 @@ class Decimal(object): if context is None: context = getcontext() - tmp = list(map(str, self._int)) + tmp = list(self._int) numdigits = len(self._int) leftdigits = self._exp + numdigits if eng and not self: # self = 0eX wants 0[.0[0]]eY, not [[0]0]0eY @@ -1030,7 +1046,7 @@ class Decimal(object): sign = min(self._sign, other._sign) if negativezero: sign = 1 - ans = Decimal( (sign, (0,), exp)) + ans = _dec_from_triple(sign, '0', exp) if shouldround: ans = ans._fix(context) return ans @@ -1055,7 +1071,7 @@ class Decimal(object): if op1.sign != op2.sign: # Equal and opposite if op1.int == op2.int: - ans = Decimal((negativezero, (0,), exp)) + ans = _dec_from_triple(negativezero, '0', exp) if shouldround: ans = ans._fix(context) return ans @@ -1121,7 +1137,7 @@ class Decimal(object): For example: Decimal('5.624e10')._increment() == Decimal('5.625e10') """ - L = list(self._int) + L = list(map(int, self._int)) L[-1] += 1 spot = len(L)-1 while L[spot] == 10: @@ -1131,7 +1147,7 @@ class Decimal(object): break L[spot-1] += 1 spot -= 1 - return Decimal((self._sign, L, self._exp)) + return _dec_from_triple(self._sign, "".join(map(str, L)), self._exp) def __mul__(self, other, context=None): """Return self * other. @@ -1167,20 +1183,20 @@ class Decimal(object): # Special case for multiplying by zero if not self or not other: - ans = Decimal((resultsign, (0,), resultexp)) + ans = _dec_from_triple(resultsign, '0', resultexp) if shouldround: # Fixing in case the exponent is out of bounds ans = ans._fix(context) return ans # Special case for multiplying by power of 10 - if self._int == (1,): - ans = Decimal((resultsign, other._int, resultexp)) + if self._int == '1': + ans = _dec_from_triple(resultsign, other._int, resultexp) if shouldround: ans = ans._fix(context) return ans - if other._int == (1,): - ans = Decimal((resultsign, self._int, resultexp)) + if other._int == '1': + ans = _dec_from_triple(resultsign, self._int, resultexp) if shouldround: ans = ans._fix(context) return ans @@ -1188,9 +1204,7 @@ class Decimal(object): op1 = _WorkRep(self) op2 = _WorkRep(other) - ans = Decimal((resultsign, - tuple(map(int, str(op1.int * op2.int))), - resultexp)) + ans = _dec_from_triple(resultsign, str(op1.int * op2.int), resultexp) if shouldround: ans = ans._fix(context) @@ -1221,7 +1235,7 @@ class Decimal(object): if other._isinfinity(): context._raise_error(Clamped, 'Division by infinity') - return Decimal((sign, (0,), context.Etiny())) + return _dec_from_triple(sign, '0', context.Etiny()) # Special cases for zeroes if not other: @@ -1253,7 +1267,7 @@ class Decimal(object): coeff //= 10 exp += 1 - ans = Decimal((sign, list(map(int, str(coeff))), exp)) + ans = _dec_from_triple(sign, str(coeff), exp) return ans._fix(context) def _divide(self, other, context): @@ -1270,7 +1284,7 @@ class Decimal(object): expdiff = self.adjusted() - other.adjusted() if not self or other._isinfinity() or expdiff <= -2: - return (Decimal((sign, (0,), 0)), + return (_dec_from_triple(sign, '0', 0), self._rescale(ideal_exp, context.rounding)) if expdiff <= context.prec: op1 = _WorkRep(self) @@ -1281,9 +1295,8 @@ class Decimal(object): op2.int *= 10**(op2.exp - op1.exp) q, r = divmod(op1.int, op2.int) if q < 10**context.prec: - return (Decimal((sign, list(map(int, str(q))), 0)), - Decimal((self._sign, list(map(int, str(r))), - ideal_exp))) + return (_dec_from_triple(sign, str(q), 0), + _dec_from_triple(self._sign, str(r), ideal_exp)) # Here the quotient is too large to be representable ans = context._raise_error(DivisionImpossible, @@ -1411,7 +1424,7 @@ class Decimal(object): # self = 0 -> remainder = self, with ideal exponent ideal_exponent = min(self._exp, other._exp) if not self: - ans = Decimal((self._sign, (0,), ideal_exponent)) + ans = _dec_from_triple(self._sign, '0', ideal_exponent) return ans._fix(context) # catch most cases of large or small quotient @@ -1448,7 +1461,7 @@ class Decimal(object): sign = 1-sign r = -r - ans = Decimal((sign, list(map(int, str(r))), ideal_exponent)) + ans = _dec_from_triple(sign, str(r), ideal_exponent) return ans._fix(context) def __floordiv__(self, other, context=None): @@ -1500,9 +1513,9 @@ class Decimal(object): raise OverflowError("Cannot convert infinity to int") s = (-1)**self._sign if self._exp >= 0: - return s*int(''.join(map(str, self._int)))*10**self._exp + return s*int(self._int)*10**self._exp else: - return s*int(''.join(map(str, self._int))[:self._exp] or '0') + return s*int(self._int[:self._exp] or '0') def _fix_nan(self, context): """Decapitate the payload of a NaN to fit the context""" @@ -1512,11 +1525,8 @@ class Decimal(object): # precision-1 if _clamp=1. max_payload_len = context.prec - context._clamp if len(payload) > max_payload_len: - pos = len(payload)-max_payload_len - while pos < len(payload) and payload[pos] == 0: - pos += 1 - payload = payload[pos:] - return Decimal((self._sign, payload, self._exp)) + payload = payload[len(payload)-max_payload_len:].lstrip('0') + return _dec_from_triple(self._sign, payload, self._exp, True) return Decimal(self) def _fix(self, context): @@ -1549,7 +1559,7 @@ class Decimal(object): new_exp = min(max(self._exp, Etiny), exp_max) if new_exp != self._exp: context._raise_error(Clamped) - return Decimal((self._sign, (0,), new_exp)) + return _dec_from_triple(self._sign, '0', new_exp) else: return Decimal(self) @@ -1581,7 +1591,8 @@ class Decimal(object): # we get here only if rescaling rounds the # cofficient up to exactly 10**context.prec if ans._exp < Etop: - ans = Decimal((ans._sign, ans._int[:-1], ans._exp+1)) + ans = _dec_from_triple(ans._sign, + ans._int[:-1], ans._exp+1) else: # Inexact and Rounded have already been raised ans = context._raise_error(Overflow, 'above Emax', @@ -1591,8 +1602,8 @@ class Decimal(object): # fold down if _clamp == 1 and self has too few digits if context._clamp == 1 and self._exp > Etop: context._raise_error(Clamped) - self_padded = self._int + (0,)*(self._exp - Etop) - return Decimal((self._sign, self_padded, Etop)) + self_padded = self._int + '0'*(self._exp - Etop) + return _dec_from_triple(self._sign, self_padded, Etop) # here self was representable to begin with; return unchanged return Decimal(self) @@ -1607,29 +1618,29 @@ class Decimal(object): def _round_down(self, prec): """Also known as round-towards-0, truncate.""" newexp = self._exp + len(self._int) - prec - return Decimal((self._sign, self._int[:prec] or (0,), newexp)) + return _dec_from_triple(self._sign, self._int[:prec] or '0', newexp) def _round_up(self, prec): """Rounds away from 0.""" newexp = self._exp + len(self._int) - prec - tmp = Decimal((self._sign, self._int[:prec] or (0,), newexp)) + tmp = _dec_from_triple(self._sign, self._int[:prec] or '0', newexp) for digit in self._int[prec:]: - if digit != 0: + if digit != '0': return tmp._increment() return tmp def _round_half_up(self, prec): """Rounds 5 up (away from 0)""" - if self._int[prec] >= 5: + if self._int[prec] in '56789': return self._round_up(prec) else: return self._round_down(prec) def _round_half_down(self, prec): """Round 5 down""" - if self._int[prec] == 5: + if self._int[prec] == '5': for digit in self._int[prec+1:]: - if digit != 0: + if digit != '0': break else: return self._round_down(prec) @@ -1637,7 +1648,7 @@ class Decimal(object): def _round_half_even(self, prec): """Round 5 to even, rest to nearest.""" - if prec and self._int[prec-1] & 1: + if prec and self._int[prec-1] in '13579': return self._round_half_up(prec) else: return self._round_half_down(prec) @@ -1658,7 +1669,7 @@ class Decimal(object): def _round_05up(self, prec): """Round down unless digit prec-1 is 0 or 5.""" - if prec == 0 or self._int[prec-1] in (0, 5): + if prec == 0 or self._int[prec-1] in '05': return self._round_up(prec) else: return self._round_down(prec) @@ -1776,7 +1787,7 @@ class Decimal(object): base = pow(base, 10, modulo) base = pow(base, exponent.int, modulo) - return Decimal((sign, list(map(int, str(base))), 0)) + return _dec_from_triple(sign, str(base), 0) def _power_exact(self, other, p): """Attempt to compute self**other exactly. @@ -1866,7 +1877,7 @@ class Decimal(object): zeros = min(exponent-ideal_exponent, p-1) else: zeros = 0 - return Decimal((0, (1,) + (0,)*zeros, exponent-zeros)) + return _dec_from_triple(0, '1' + '0'*zeros, exponent-zeros) # case where y is negative: xc must be either a power # of 2 or a power of 5. @@ -1927,7 +1938,7 @@ class Decimal(object): if xc >= 10**p: return None xe = -e-xe - return Decimal((0, list(map(int, str(xc))), xe)) + return _dec_from_triple(0, str(xc), xe) # now y is positive; find m and n such that y = m/n if ye >= 0: @@ -1989,7 +2000,7 @@ class Decimal(object): zeros = min(xe-ideal_exponent, p-len(str_xc)) else: zeros = 0 - return Decimal((0, list(map(int, str_xc))+[0,]*zeros, xe-zeros)) + return _dec_from_triple(0, str_xc+'0'*zeros, xe-zeros) def __pow__(self, other, modulo=None, context=None): """Return self ** other [ % modulo]. @@ -2050,12 +2061,12 @@ class Decimal(object): return context._raise_error(InvalidOperation, 'x ** y with x negative and y not an integer') # negate self, without doing any unwanted rounding - self = Decimal((0, self._int, self._exp)) + self = self.copy_negate() # 0**(+ve or Inf)= 0; 0**(-ve or -Inf) = Infinity if not self: if other._sign == 0: - return Decimal((result_sign, (0,), 0)) + return _dec_from_triple(result_sign, '0', 0) else: return Infsign[result_sign] @@ -2064,7 +2075,7 @@ class Decimal(object): if other._sign == 0: return Infsign[result_sign] else: - return Decimal((result_sign, (0,), 0)) + return _dec_from_triple(result_sign, '0', 0) # 1**other = 1, but the choice of exponent and the flags # depend on the exponent of self, and on whether other is a @@ -2091,7 +2102,7 @@ class Decimal(object): context._raise_error(Rounded) exp = 1-context.prec - return Decimal((result_sign, (1,)+(0,)*-exp, exp)) + return _dec_from_triple(result_sign, '1'+'0'*-exp, exp) # compute adjusted exponent of self self_adj = self.adjusted() @@ -2100,7 +2111,7 @@ class Decimal(object): # self ** -infinity is infinity if self < 1, 0 if self > 1 if other._isinfinity(): if (other._sign == 0) == (self_adj < 0): - return Decimal((result_sign, (0,), 0)) + return _dec_from_triple(result_sign, '0', 0) else: return Infsign[result_sign] @@ -2118,19 +2129,19 @@ class Decimal(object): # self > 1 and other +ve, or self < 1 and other -ve # possibility of overflow if bound >= len(str(context.Emax)): - ans = Decimal((result_sign, (1,), context.Emax+1)) + ans = _dec_from_triple(result_sign, '1', context.Emax+1) else: # self > 1 and other -ve, or self < 1 and other +ve # possibility of underflow to 0 Etiny = context.Etiny() if bound >= len(str(-Etiny)): - ans = Decimal((result_sign, (1,), Etiny-1)) + ans = _dec_from_triple(result_sign, '1', Etiny-1) # try for an exact result with precision +1 if ans is None: ans = self._power_exact(other, context.prec + 1) if ans is not None and result_sign == 1: - ans = Decimal((1, ans._int, ans._exp)) + ans = _dec_from_triple(1, ans._int, ans._exp) # usual case: inexact result, x**y computed directly as exp(y*log(x)) if ans is None: @@ -2151,7 +2162,7 @@ class Decimal(object): break extra += 3 - ans = Decimal((result_sign, list(map(int, str(coeff))), exp)) + ans = _dec_from_triple(result_sign, str(coeff), exp) # the specification says that for non-integer other we need to # raise Inexact, even when the result is actually exact. In @@ -2163,7 +2174,8 @@ class Decimal(object): # pad with zeros up to length context.prec+1 if necessary if len(ans._int) <= context.prec: expdiff = context.prec+1 - len(ans._int) - ans = Decimal((ans._sign, ans._int+(0,)*expdiff, ans._exp-expdiff)) + ans = _dec_from_triple(ans._sign, ans._int+'0'*expdiff, + ans._exp-expdiff) if ans.adjusted() < context.Emin: context._raise_error(Underflow) @@ -2195,14 +2207,14 @@ class Decimal(object): return dup if not dup: - return Decimal( (dup._sign, (0,), 0) ) + return _dec_from_triple(dup._sign, '0', 0) exp_max = [context.Emax, context.Etop()][context._clamp] end = len(dup._int) exp = dup._exp - while dup._int[end-1] == 0 and exp < exp_max: + while dup._int[end-1] == '0' and exp < exp_max: exp += 1 end -= 1 - return Decimal( (dup._sign, dup._int[:end], exp) ) + return _dec_from_triple(dup._sign, dup._int[:end], exp) def quantize(self, exp, rounding=None, context=None, watchexp=True): """Quantize self so its exponent is the same as that of exp. @@ -2243,7 +2255,7 @@ class Decimal(object): 'target exponent out of bounds in quantize') if not self: - ans = Decimal((self._sign, (0,), exp._exp)) + ans = _dec_from_triple(self._sign, '0', exp._exp) return ans._fix(context) self_adjusted = self.adjusted() @@ -2303,17 +2315,18 @@ class Decimal(object): if self._is_special: return Decimal(self) if not self: - return Decimal((self._sign, (0,), exp)) + return _dec_from_triple(self._sign, '0', exp) if self._exp >= exp: # pad answer with zeros if necessary - return Decimal((self._sign, self._int + (0,)*(self._exp - exp), exp)) + return _dec_from_triple(self._sign, + self._int + '0'*(self._exp - exp), exp) # too many digits; round and lose data. If self.adjusted() < # exp-1, replace self by 10**(exp-1) before rounding digits = len(self._int) + self._exp - exp if digits < 0: - self = Decimal((self._sign, (1,), exp-1)) + self = _dec_from_triple(self._sign, '1', exp-1) digits = 0 this_function = getattr(self, self._pick_rounding_function[rounding]) return this_function(digits) @@ -2336,7 +2349,7 @@ class Decimal(object): if self._exp >= 0: return Decimal(self) if not self: - return Decimal((self._sign, (0,), 0)) + return _dec_from_triple(self._sign, '0', 0) if context is None: context = getcontext() if rounding is None: @@ -2378,7 +2391,7 @@ class Decimal(object): if not self: # exponent = self._exp // 2. sqrt(-0) = -0 - ans = Decimal((self._sign, (0,), self._exp // 2)) + ans = _dec_from_triple(self._sign, '0', self._exp // 2) return ans._fix(context) if context is None: @@ -2455,7 +2468,7 @@ class Decimal(object): if n % 5 == 0: n += 1 - ans = Decimal((0, list(map(int, str(n))), e)) + ans = _dec_from_triple(0, str(n), e) # round, and fit to current context context = context._shallow_copy() @@ -2552,13 +2565,13 @@ class Decimal(object): if self._exp >= 0: return True rest = self._int[self._exp:] - return rest == (0,)*len(rest) + return rest == '0'*len(rest) def _iseven(self): """Returns True if self is even. Assumes self is an integer.""" if not self or self._exp > 0: return True - return self._int[-1+self._exp] & 1 == 0 + return self._int[-1+self._exp] in '02468' def adjusted(self): """Return the adjusted exponent of self""" @@ -2680,18 +2693,19 @@ class Decimal(object): def copy_abs(self): """Returns a copy with the sign set to 0. """ - return Decimal((0, self._int, self._exp)) + return _dec_from_triple(0, self._int, self._exp, self._is_special) def copy_negate(self): """Returns a copy with the sign inverted.""" if self._sign: - return Decimal((0, self._int, self._exp)) + return _dec_from_triple(0, self._int, self._exp, self._is_special) else: - return Decimal((1, self._int, self._exp)) + return _dec_from_triple(1, self._int, self._exp, self._is_special) def copy_sign(self, other): """Returns self with the sign of other.""" - return Decimal((other._sign, self._int, self._exp)) + return _dec_from_triple(other._sign, self._int, + self._exp, self._is_special) def exp(self, context=None): """Returns e ** self.""" @@ -2730,16 +2744,16 @@ class Decimal(object): # larger exponent the result either overflows or underflows. if self._sign == 0 and adj > len(str((context.Emax+1)*3)): # overflow - ans = Decimal((0, (1,), context.Emax+1)) + ans = _dec_from_triple(0, '1', context.Emax+1) elif self._sign == 1 and adj > len(str((-context.Etiny()+1)*3)): # underflow to 0 - ans = Decimal((0, (1,), context.Etiny()-1)) + ans = _dec_from_triple(0, '1', context.Etiny()-1) elif self._sign == 0 and adj < -p: # p+1 digits; final round will raise correct flags - ans = Decimal((0, (1,) + (0,)*(p-1) + (1,), -p)) + ans = _dec_from_triple(0, '1' + '0'*(p-1) + '1', -p) elif self._sign == 1 and adj < -p-1: # p+1 digits; final round will raise correct flags - ans = Decimal((0, (9,)*(p+1), -p-1)) + ans = _dec_from_triple(0, '9'*(p+1), -p-1) # general case else: op = _WorkRep(self) @@ -2757,7 +2771,7 @@ class Decimal(object): break extra += 3 - ans = Decimal((0, list(map(int, str(coeff))), exp)) + ans = _dec_from_triple(0, str(coeff), exp) # at this stage, ans should round correctly with *any* # rounding mode, not just with ROUND_HALF_EVEN @@ -2822,7 +2836,7 @@ class Decimal(object): def is_zero(self): """Return True if self is a zero; otherwise return False.""" - return not self._is_special and self._int[0] == 0 + return not self._is_special and self._int == '0' def _ln_exp_bound(self): """Compute a lower bound for the adjusted exponent of self.ln(). @@ -2891,7 +2905,7 @@ class Decimal(object): if coeff % (5*10**(len(str(abs(coeff)))-p-1)): break places += 3 - ans = Decimal((int(coeff<0), list(map(int, str(abs(coeff)))), -places)) + ans = _dec_from_triple(int(coeff<0), str(abs(coeff)), -places) context = context._shallow_copy() rounding = context._set_rounding(ROUND_HALF_EVEN) @@ -2954,7 +2968,7 @@ class Decimal(object): 'log10 of a negative value') # log10(10**n) = n - if self._int[0] == 1 and self._int[1:] == (0,)*(len(self._int) - 1): + if self._int[0] == '1' and self._int[1:] == '0'*(len(self._int) - 1): # answer may need rounding ans = Decimal(self._exp + len(self._int) - 1) else: @@ -2972,8 +2986,7 @@ class Decimal(object): if coeff % (5*10**(len(str(abs(coeff)))-p-1)): break places += 3 - ans = Decimal((int(coeff<0), list(map(int, str(abs(coeff)))), - -places)) + ans = _dec_from_triple(int(coeff<0), str(abs(coeff)), -places) context = context._shallow_copy() rounding = context._set_rounding(ROUND_HALF_EVEN) @@ -3020,19 +3033,19 @@ class Decimal(object): if self._sign != 0 or self._exp != 0: return False for dig in self._int: - if dig not in (0, 1): + if dig not in '01': return False return True def _fill_logical(self, context, opa, opb): dif = context.prec - len(opa) if dif > 0: - opa = (0,)*dif + opa + opa = '0'*dif + opa elif dif < 0: opa = opa[-context.prec:] dif = context.prec - len(opb) if dif > 0: - opb = (0,)*dif + opb + opb = '0'*dif + opb elif dif < 0: opb = opb[-context.prec:] return opa, opb @@ -3048,22 +3061,15 @@ class Decimal(object): (opa, opb) = self._fill_logical(context, self._int, other._int) # make the operation, and clean starting zeroes - result = [a&b for a,b in zip(opa,opb)] - for i,d in enumerate(result): - if d == 1: - break - result = tuple(result[i:]) - - # if empty, we must have at least a zero - if not result: - result = (0,) - return Decimal((0, result, 0)) + result = "".join([str(int(a)&int(b)) for a,b in zip(opa,opb)]) + return _dec_from_triple(0, result.lstrip('0') or '0', 0) def logical_invert(self, context=None): """Invert all its digits.""" if context is None: context = getcontext() - return self.logical_xor(Decimal((0,(1,)*context.prec,0)), context) + return self.logical_xor(_dec_from_triple(0,'1'*context.prec,0), + context) def logical_or(self, other, context=None): """Applies an 'or' operation between self and other's digits.""" @@ -3076,16 +3082,8 @@ class Decimal(object): (opa, opb) = self._fill_logical(context, self._int, other._int) # make the operation, and clean starting zeroes - result = [a|b for a,b in zip(opa,opb)] - for i,d in enumerate(result): - if d == 1: - break - result = tuple(result[i:]) - - # if empty, we must have at least a zero - if not result: - result = (0,) - return Decimal((0, result, 0)) + result = "".join(str(int(a)|int(b)) for a,b in zip(opa,opb)) + return _dec_from_triple(0, result.lstrip('0') or '0', 0) def logical_xor(self, other, context=None): """Applies an 'xor' operation between self and other's digits.""" @@ -3098,16 +3096,8 @@ class Decimal(object): (opa, opb) = self._fill_logical(context, self._int, other._int) # make the operation, and clean starting zeroes - result = [a^b for a,b in zip(opa,opb)] - for i,d in enumerate(result): - if d == 1: - break - result = tuple(result[i:]) - - # if empty, we must have at least a zero - if not result: - result = (0,) - return Decimal((0, result, 0)) + result = "".join(str(int(a)^int(b)) for a,b in zip(opa,opb)) + return _dec_from_triple(0, result.lstrip('0') or '0', 0) def max_mag(self, other, context=None): """Compares the values numerically with their sign ignored.""" @@ -3185,7 +3175,7 @@ class Decimal(object): if self._isinfinity() == -1: return negInf if self._isinfinity() == 1: - return Decimal((0, (9,)*context.prec, context.Etop())) + return _dec_from_triple(0, '9'*context.prec, context.Etop()) context = context.copy() context._set_rounding(ROUND_FLOOR) @@ -3193,7 +3183,8 @@ class Decimal(object): new_self = self._fix(context) if new_self != self: return new_self - return self.__sub__(Decimal((0, (1,), context.Etiny()-1)), context) + return self.__sub__(_dec_from_triple(0, '1', context.Etiny()-1), + context) def next_plus(self, context=None): """Returns the smallest representable number larger than itself.""" @@ -3207,7 +3198,7 @@ class Decimal(object): if self._isinfinity() == 1: return Inf if self._isinfinity() == -1: - return Decimal((1, (9,)*context.prec, context.Etop())) + return _dec_from_triple(1, '9'*context.prec, context.Etop()) context = context.copy() context._set_rounding(ROUND_CEILING) @@ -3215,7 +3206,8 @@ class Decimal(object): new_self = self._fix(context) if new_self != self: return new_self - return self.__add__(Decimal((0, (1,), context.Etiny()-1)), context) + return self.__add__(_dec_from_triple(0, '1', context.Etiny()-1), + context) def next_toward(self, other, context=None): """Returns the number closest to self, in the direction towards other. @@ -3237,7 +3229,7 @@ class Decimal(object): comparison = self.__cmp__(other) if comparison == 0: - return Decimal((other._sign, self._int, self._exp)) + return self.copy_sign(other) if comparison == -1: ans = self.next_plus(context) @@ -3331,19 +3323,12 @@ class Decimal(object): rotdig = self._int topad = context.prec - len(rotdig) if topad: - rotdig = ((0,)*topad) + rotdig + rotdig = '0'*topad + rotdig # let's rotate! rotated = rotdig[torot:] + rotdig[:torot] - - # clean starting zeroes - for i,d in enumerate(rotated): - if d != 0: - break - rotated = rotated[i:] - - return Decimal((self._sign, rotated, self._exp)) - + return _dec_from_triple(self._sign, + rotated.lstrip('0') or '0', self._exp) def scaleb (self, other, context=None): """Returns self operand after adding the second value to its exp.""" @@ -3364,7 +3349,7 @@ class Decimal(object): if self._isinfinity(): return Decimal(self) - d = Decimal((self._sign, self._int, self._exp + int(other))) + d = _dec_from_triple(self._sign, self._int, self._exp + int(other)) d = d._fix(context) return d @@ -3392,26 +3377,17 @@ class Decimal(object): rotdig = self._int topad = context.prec - len(rotdig) if topad: - rotdig = ((0,)*topad) + rotdig + rotdig = '0'*topad + rotdig # let's shift! if torot < 0: rotated = rotdig[:torot] else: - rotated = (rotdig + ((0,) * torot)) + rotated = rotdig + '0'*torot rotated = rotated[-context.prec:] - # clean starting zeroes - if rotated: - for i,d in enumerate(rotated): - if d != 0: - break - rotated = rotated[i:] - else: - rotated = (0,) - - return Decimal((self._sign, rotated, self._exp)) - + return _dec_from_triple(self._sign, + rotated.lstrip('0') or '0', self._exp) # Support for pickling, copy, and deepcopy def __reduce__(self): @@ -3427,6 +3403,22 @@ class Decimal(object): return self # My components are also immutable return self.__class__(str(self)) +def _dec_from_triple(sign, coefficient, exponent, special=False): + """Create a decimal instance directly, without any validation, + normalization (e.g. removal of leading zeros) or argument + conversion. + + This function is for *internal use only*. + """ + + self = object.__new__(Decimal) + self._sign = sign + self._int = coefficient + self._exp = exponent + self._is_special = special + + return self + ##### Context class ####################################################### @@ -4775,10 +4767,7 @@ class _WorkRep(object): self.exp = None elif isinstance(value, Decimal): self.sign = value._sign - cum = 0 - for digit in value._int: - cum = cum * 10 + digit - self.int = cum + self.int = int(value._int) self.exp = value._exp else: # assert isinstance(value, tuple) @@ -5175,53 +5164,6 @@ def _convert_other(other, raiseit=False): raise TypeError("Unable to convert %s to Decimal" % other) return NotImplemented -_infinity_map = { - 'inf' : 1, - 'infinity' : 1, - '+inf' : 1, - '+infinity' : 1, - '-inf' : -1, - '-infinity' : -1 -} - -def _isinfinity(num): - """Determines whether a string or float is infinity. - - +1 for negative infinity; 0 for finite ; +1 for positive infinity - """ - num = str(num).lower() - return _infinity_map.get(num, 0) - -def _isnan(num): - """Determines whether a string or float is NaN - - (1, sign, diagnostic info as string) => NaN - (2, sign, diagnostic info as string) => sNaN - 0 => not a NaN - """ - num = str(num).lower() - if not num: - return 0 - - # Get the sign, get rid of trailing [+-] - sign = 0 - if num[0] == '+': - num = num[1:] - elif num[0] == '-': # elif avoids '+-nan' - num = num[1:] - sign = 1 - - if num.startswith('nan'): - if len(num) > 3 and not num[3:].isdigit(): # diagnostic info - return 0 - return (1, sign, num[3:].lstrip('0')) - if num.startswith('snan'): - if len(num) > 4 and not num[4:].isdigit(): - return 0 - return (2, sign, num[4:].lstrip('0')) - return 0 - - ##### Setup Specific Contexts ############################################ # The default context prototype used by Context() @@ -5255,91 +5197,62 @@ ExtendedContext = Context( ) -##### Useful Constants (internal use only) ################################ - -# Reusable defaults -Inf = Decimal('Inf') -negInf = Decimal('-Inf') -NaN = Decimal('NaN') -Dec_0 = Decimal(0) -Dec_p1 = Decimal(1) -Dec_n1 = Decimal(-1) -Dec_p2 = Decimal(2) -Dec_n2 = Decimal(-2) - -# Infsign[sign] is infinity w/ that sign -Infsign = (Inf, negInf) - - ##### crud for parsing strings ############################################# import re -# There's an optional sign at the start, and an optional exponent -# at the end. The exponent has an optional sign and at least one -# digit. In between, must have either at least one digit followed -# by an optional fraction, or a decimal point followed by at least -# one digit. Yuck. +# Regular expression used for parsing numeric strings. Additional +# comments: +# +# 1. Uncomment the two '\s*' lines to allow leading and/or trailing +# whitespace. But note that the specification disallows whitespace in +# a numeric string. +# +# 2. For finite numbers (not infinities and NaNs) the body of the +# number between the optional sign and the optional exponent must have +# at least one decimal digit, possibly after the decimal point. The +# lookahead expression '(?=\d|\.\d)' checks this. +# +# As the flag UNICODE is not enabled here, we're explicitly avoiding any +# other meaning for \d than the numbers [0-9]. -_parser = re.compile(r""" +import re +_parser = re.compile(r""" # A numeric string consists of: # \s* - (?P<sign>[-+])? + (?P<sign>[-+])? # an optional sign, followed by either... ( - (?P<int>\d+) (\. (?P<frac>\d*))? + (?=\d|\.\d) # ...a number (with at least one digit) + (?P<int>\d*) # consisting of a (possibly empty) integer part + (\.(?P<frac>\d*))? # followed by an optional fractional part + (E(?P<exp>[-+]?\d+))? # followed by an optional exponent, or... | - \. (?P<onlyfrac>\d+) + Inf(inity)? # ...an infinity, or... + | + (?P<signal>s)? # ...an (optionally signaling) + NaN # NaN + (?P<diag>\d*) # with (possibly empty) diagnostic information. ) - ([eE](?P<exp>[-+]? \d+))? # \s* $ -""", re.VERBOSE).match # Uncomment the \s* to allow leading or trailing spaces. +""", re.VERBOSE | re.IGNORECASE).match del re -def _string2exact(s): - """Return sign, n, p s.t. - Float string value == -1**sign * n * 10**p exactly - """ - m = _parser(s) - if m is None: - raise ValueError("invalid literal for Decimal: %r" % s) +##### Useful Constants (internal use only) ################################ - if m.group('sign') == "-": - sign = 1 - else: - sign = 0 +# Reusable defaults +Inf = Decimal('Inf') +negInf = Decimal('-Inf') +NaN = Decimal('NaN') +Dec_0 = Decimal(0) +Dec_p1 = Decimal(1) +Dec_n1 = Decimal(-1) +Dec_p2 = Decimal(2) +Dec_n2 = Decimal(-2) - exp = m.group('exp') - if exp is None: - exp = 0 - else: - exp = int(exp) +# Infsign[sign] is infinity w/ that sign +Infsign = (Inf, negInf) - intpart = m.group('int') - if intpart is None: - intpart = "" - fracpart = m.group('onlyfrac') - else: - fracpart = m.group('frac') - if fracpart is None: - fracpart = "" - - exp -= len(fracpart) - - mantissa = intpart + fracpart - tmp = list(map(int, mantissa)) - backup = tmp - while tmp and tmp[0] == 0: - del tmp[0] - - # It's a zero - if not tmp: - if backup: - return (sign, tuple(backup), exp) - return (sign, (0,), exp) - mantissa = tuple(tmp) - - return (sign, mantissa, exp) if __name__ == '__main__': |