A Bug By Any Other Name ...

Gary Herron gherron at islandtraining.com
Mon Jul 6 02:33:36 EDT 2009

Gabriel Genellina wrote:
> En Mon, 06 Jul 2009 00:28:43 -0300, Steven D'Aprano 
> <steve at remove-this-cybersource.com.au> escribió:
>> On Mon, 06 Jul 2009 14:32:46 +1200, Lawrence D'Oliveiro wrote:
>>> I wonder how many people have been tripped up by the fact that
>>>     ++n
>>> and
>>>     --n
>>> fail silently for numeric-valued n.
>> What do you mean, "fail silently"? They do exactly what you should 
>> expect:
>>>>> ++5  # positive of a positive number is positive
>> I'm not sure what "bug" you're seeing. Perhaps it's your expectations
>> that are buggy, not Python.
> Well, those expectations are taken seriously when new features are 
> introduced into the language - and sometimes the feature is dismissed 
> just because it would be confusing for some.
> If a += 1 works, expecting ++a to have the same meaning is very 
> reasonable (for those coming from languages with a ++ operator, like C 
> or Java) - more when ++a is a perfectly valid expression.
> If this issue isn't listed under the various "Python gotchas" 
> articles, it should...

Well sure, it's not unreasonable to expect ++n and --n to behave as in 
other languages, and since they don't, perhaps they should be listed as 
a "Python gotcha". 

But even so, it's quite arrogant of the OP to flaunt his ignorance of 
the language by claiming this is a bug and a failure.  It shouldn't have 
been all that hard for him to figure out what was really happening.

Gary Herron

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