Subject: Re: [boost] [type_traits][function_types] Discard param const qualification, bug or feature?
From: Jonathan Wakely (jwakely.boost_at_[hidden])
Date: 2013-10-01 03:30:02
On 1 October 2013 05:45, Mostafa wrote:
> On Mon, 30 Sep 2013 19:54:56 -0700, Gavin Lambert wrote:
>> A simple add_reference is obviously the wrong thing to be doing then.
>> In general, you can take any parameter type T and wrap it as a "const T&"
>> (or if you prefer, "T const&") and it will do the right thing, unless T was
>> already a reference. But note that you must use a const reference -- a
>> non-const reference won't work.
> Not in my particular use case. The code I was working is generated by a mix
> of PPMP and TMP techniques. The argument x is eventually forwarded to some
> user block of code, where the user expects it to be of the same type as the
> one he/she specified in the signature of SomeUserClass::foo. So had the user
> specified this instead:
> struct SomeUserClass
> static void foo(int x)
> Then it is expected that x would be mutable in that forwarded-to block of
Well then you're doing it wrong. You should base the forwarded
parameter type on decltype(x) not the parameter type in the function
signature. The function signature doesn't include the top-level
const, that's how C++ works.