Re: [lambda] Segmentation fault in simple lambda program

[John Freeman <jfreeman08@gmail.com>]

Jason Merrill wrote:
>> Experimenting with a working version and seeing it's issues will be 
>> useful to me.  To others to maybe.  With concepts
>> gone from C++0x and being reworked for C++15(?) maybe support for 
>> polymorphic lambdas could be reintroduced? -- though
>> I'm sure its much too late for that and that its likely been around 
>> the buoy many times.  From what I have read I got
>> the idea that the Callable concept was the primary reason for 
>> polymorphic lambdas not being accepted.
>
> I don't know what the reasoning was there, but people have been 
> somewhat conservative about what usages of lambdas are allowed for 
> fear of unforseen implementation issues.  Certainly having a working 
> implementation would go a lot toward convincing people to allow it, 
> even if it doesn't make it into C++0x.

There were several issues with polymorphic lambdas in the presence of 
concepts that concerned many on the committee.  I've come to accept that 
it's too late to re-introduce polymorphic lambdas into C++0x (now 
C++1x), but there's no stopping GCC from implementing it as an extension.

>
>
>> Implied template typename arguments via auto are not currently 
>> supported.  The syntax parses but I haven't yet
>> synthesized the template arguments and therefore not replaced the 
>> auto's with them so it doesn't compile.
>
> Since templates work so differently from normal functions, I'm a 
> little uncomfortable with the idea of templates that don't involve any 
> template syntax, just the use of auto in the parameter list.  But I'm 
> open to giving it a try, at least in the lambda context.  Maybe 
> outside of lambda it could be used with a small template introducer...

Just my opinion, but I don't think there should be any special template 
syntax.  The whole point of argument deduction was terseness.  It 
doesn't have to be implemented using templates, so I don't equate it 
with templates.

- John