[Python-ideas] Implicit string literal concatenation considered harmful?

[MRAB]

On 16/05/2013 16:57, Andrew Barnert wrote:
> On May 16, 2013, at 8:00, MRAB <python at mrabarnett.plus.com> wrote:
>
>> On 16/05/2013 15:44, Chris Angelico wrote:
>>> On Fri, May 17, 2013 at 12:40 AM, MRAB
>>> <python at mrabarnett.plus.com> wrote:
>>>> On 16/05/2013 08:08, Serhiy Storchaka wrote:
>>>>> As was said before the '+' operator has less priority than
>>>>> the '%' operator and an attribute access, i.e. it requires
>>>>> parenthesis in some cases. However parenthesis introduce a
>>>>> noise and can cause other types of errors.
>>>> I wonder whether we could use ".". Or would that be too
>>>> confusing?
>
>>> And I apologized for borrowing an idea from bash. Taking an idea
>>> from PHP?!?
>> It has high precendence as far as the parser is concerned.
>>
>> I know that Perl uses it. I haven't looked at PHP (I hear bad
>> things about it! :-)).
>>
>>> Seriously, I don't think another operator is needed. If it's not
>>> going to be the implicit concatenation by abuttal, + or \ will
>>> carry the matter. But I share the opinion of several here:
>>> implicit concatenation is not as bad as the alternatives.
>> It wouldn't be an operator as such
>
> Of course in php, perl, and every other language that uses dot for
> string concatenation, it _is_ an operator, so this will end up
> confusing the very people who initially find it comforting.
>
> And this means the parser has to figure out whether you mean dot for
> attribute access or dot for concatenation. That's not exactly a
> _hard_ problem, but it's not _trivial_.
>
> And then there's the fact that the "precedence" is different
> depending on which meaning the dot gets. Remember that what you're
> trying to solve is the problem that member-dot and % both have higher
> precedence than +.
>
I thought the problem we were trying to solve was that "+" has a lower
precedence than "%" and attribute/method access, so implicit
concatenation that's followed by "%" or ".format" can't be replaced by
"+" without adding extra parentheses.