Facundo Batista <facundobati...@gmail.com> wrote:
> On Fri, Mar 19, 2010 at 5:50 PM, Guido van Rossum <gu...@python.org> wrote:
>
> > As a downside, there is the worry that inadvertent mixing of Decimal
> > and float can compromise the correctness of programs in a way that is
> > hard to detect. But the anomalies above indicate that not fixing the
>
> Decimal already has something that we can use in this case, and fits
> very nice here: Signals.
I like the simplicity of having a single signal (e.g. CoercionError), but
a strictness context flag could offer greater control for people who only
want pure decimal/integer operations.
For example:
strictness 0: completely promiscuous behaviour
strictness 1: current py3k behaviour
strictness 2: current py3k behaviour + pure equality comparisons
strictness 3: current py3k behaviour + pure equality comparisons +
disallow NaN equality comparisons [1]
Just as an illustration, here is a quick and dirty diff using the
DefaultContext for simplicity:
Index: Lib/decimal.py
===================================================================
--- Lib/decimal.py (revision 78352)
+++ Lib/decimal.py (working copy)
@@ -3765,8 +3765,8 @@
def __init__(self, prec=None, rounding=None,
traps=None, flags=None,
Emin=None, Emax=None,
- capitals=None, _clamp=0,
- _ignored_flags=None):
+ capitals=None, strictness=1,
+ _clamp=0, _ignored_flags=None):
if flags is None:
flags = []
if _ignored_flags is None:
@@ -5785,7 +5785,9 @@
return other
if isinstance(other, int):
return Decimal(other)
- if raiseit:
+ if isinstance(other, float) and DefaultContext.strictness == 0:
+ return Decimal.from_float(other)
+ if raiseit or DefaultContext.strictness > 1:
raise TypeError("Unable to convert %s to Decimal" % other)
return NotImplemented
@@ -5800,7 +5802,8 @@
flags=[],
Emax=999999999,
Emin=-999999999,
- capitals=1
+ capitals=1,
+ strictness=1
)
Stefan Krah
[1] See: http://mail.python.org/pipermail/python-dev/2009-November/093910.html,
http://mail.python.org/pipermail/python-dev/2009-November/093952.html
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