Re: [Boost-users] Problems using for_each

Subject: Re: [Boost-users] Problems using for_each
From: Will Mason (willchido_at_[hidden])
Date: 2013-03-31 14:49:59

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;

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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