Re: [Boost-users] Problems using for_each

Subject: Re: [Boost-users] Problems using for_each
From: Michael Powell (mwpowellhtx_at_[hidden])
Date: 2013-03-31 16:03:46

On Sun, Mar 31, 2013 at 1:49 PM, Will Mason <willchido_at_[hidden]> wrote:

> Hello,
>
>
> On Sun, Mar 31, 2013 at 12:20 PM, Michael Powell <mwpowellhtx_at_[hidden]>wrote:
>
>> On Sun, Mar 31, 2013 at 12:08 PM, Will Mason <willchido_at_[hidden]> wrote:
>> > Hello,
>> >
>> >
>> > On Sun, Mar 31, 2013 at 10:56 AM, Michael Powell <mwpowellhtx_at_[hidden]
>> >
>> > wrote:
>> >>
>> >> Hello,
>> >>
>> >> I am struggling making for_each work right. I am using Sourcery
>> >> targeting ARM. AFAIK, GCC is actually 4.7.2, and I am flagging
>> >> -std=c++11.
>> >>
>> >> I'm not really picky how we get for_each done (or constructs like it).
>> >> I'd like to avoid "macro-expansion" for obvious reasons (i.e. debug),
>> >> and the always-infamous verbosity of a for loop, if possible.
>> >>
>> >> I've got the following:
>> >>
>> >> vector<rgb_type*> all;
>> >> rgb_type rgb;
>> >> rgb_type rgb2 = rgb.clone();
>> >>
>> >> for_each(all.begin(), all.end(), cout << _1->r() << endl);
>> >
>> >
>> > Since you are using gcc 4.7.2 with -std=c++11, you can just use a std
>> lambda
>> > here:
>> >
>> > std::for_each(all.begin(), all.end(), [] (rgb_type* val) { std::cout <<
>> val->r() << std::endl; });
>>
>> Yessir, I believe that will work. Possibly also std::bind as needs be.
>>
>> A little refresher for me, []: return value (void implied), ():
>> captured function args (with in/out/inout rules), {}: lambda body.
>>
>
> Also, it occurs to me that, depending on your personal stylistic
> preferences, you could do the following with about the same level of
> verbosity:
>
> for (auto val : all)
>     std::cout << val->r() << std::endl;
>

Or,

for (rgb_type_pointer prgb : all) std::cout << prgb->r() << std::endl;

Where,

typedef rgb_type* rgb_type_pointer;

Sourcery seems happy with that, or at least no syntax is highlighting.

Cheers,
> Will
>
>
>>
>> I think what I am also finding is Sourcery code highlighting,
>> so-called "Semantic Errors" isn't quite in alignment with current C++
>> language standards.
>>
>> Thank ye.
>>
>> > Cheers,
>> > Will
>> >
>> >
>> >>
>> >>
>> >> With errors:
>> >>
>> >> _1 was not declared in this scope. (C++ Problem)
>> >>
>> >> That or,
>> >>
>> >> void rgb_printer_func(rgb_type* prgb) {
>> >>   cout << prgb->r() << endl;
>> >> }
>> >>
>> >> for_each(all.begin(), all.end(), rgb_printer_func);
>> >>
>> >> With errors:
>> >>
>> >> Invalid arguments Candidates are: #1 for_each(#0, #0, #1) (Semantic
>> Error)
>> >>
>> >> Thank you.
>> >>
>> >> Regards,
>> >>
>> >> Michael Powell
>> >> _______________________________________________
>> >> Boost-users mailing list
>> >> Boost-users_at_[hidden]
>> >> http://lists.boost.org/mailman/listinfo.cgi/boost-users
>> >
>> >
>> >
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>
>
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