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

[Andrew Barnert]

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 +.