[Python-checkins] r55138 - python/branches/decimal-branch/Lib/decimal.py

Fri May 4 23:00:54 CEST 2007

Author: facundo.batista
Date: Fri May 4 23:00:49 2007
New Revision: 55138
Modified:
 python/branches/decimal-branch/Lib/decimal.py
Log:
Added a private function _islogical(), which determines if the 
operand is a logical one or not. Also coded the logical_invert()
operation, which passes all tests ok.
Modified: python/branches/decimal-branch/Lib/decimal.py
==============================================================================

--- python/branches/decimal-branch/Lib/decimal.py	(original)
+++ python/branches/decimal-branch/Lib/decimal.py	Fri May 4 23:00:49 2007
@@ -2429,11 +2429,53 @@
 without limiting the resulting exponent).
 """
 
+ def _islogical(self):
+ """Return 1 is self is a logical operand.
+
+ For being logical, it must be a finite numbers with a sign of 0,
+ an exponent of 0, and a coefficient whose digits must all be
+ either 0 or 1.
+ """
+ if self._sign != 0 or self._exp != 0:
+ return 0
+ for dig in self._int:
+ if dig not in (0, 1):
+ return 0
+ return 1
+
 def logical_and(self, other, context=None):
 """Applies an 'and' operation between self and other's digits."""
 
 def logical_invert(self, context=None):
 """Invert all its digits."""
+ if context is None:
+ context = getcontext()
+
+ if not self._islogical():
+ return context._raise_error(InvalidOperation)
+
+ # fill to context.prec
+ dif = context.prec - len(self._int)
+ if dif:
+ self._int = (0,)*dif + self._int
+
+ # invert, only starting after the first resulting 1
+ result = []
+ started = False
+ for dig in self._int:
+ if dig == 1 and not started:
+ continue
+ if dig == 1:
+ result.append(0)
+ else:
+ result.append(1)
+ started = True
+ result = tuple(result)
+
+ # if empty, we must have at least a zero
+ if not result:
+ result = (0,)
+ return Decimal((0, result, 0))
 
 def logical_or(self, other, context=None):
 """Applies an 'or' operation between self and other's digits."""
