Re: [boost] [functors] proposal

Subject: Re: [boost] [functors] proposal
From: Piotr Wygocki (vwygos_at_[hidden])
Date: 2013-10-23 07:27:52

Hi Kris, thank for your feedback and code!

Particularly thanks for boost::make_function_output_iterator, I didn't know
about it!
As I wrote before my main goal is many cases is standarization. I always
prefer to use

std::less<int> (now, my nontemplate Less) than writing even a tiny lambda.

There is another think I noticed. The compile time of your example is
6,5 times bigger than the compile time of the original example (clang 3.3,
4,5 secondsto 0.7 second).

Regards,
Piotr

On 23 October 2013 12:33, Krzysztof Czainski <1czajnik_at_[hidden]> wrote:

> 2013/10/23 Edward Diener <eldiener_at_[hidden]>
>
> > On 10/22/2013 4:16 PM, Piotr Wygocki wrote:
> >
> >> Hi, I've developed a small set of functors and functor adaptors.
> >> Although this code is very simple it might be very useful for some
> subset
> >> of the community.
> >>
> >> Do you think it might become a part of the boost library?
> >> If not I'm still very interested in any feedback.
> >> I think it's not big enough to be a separate library.
> >> To my knowledge of boost it fits in the utility lib.
> >>
> >> The code can be found here:
> >>
> >> https://github.com/wygos/**functors <https://github.com/wygos/functors>
> >>
> >> List of utilities:
> >>
> >> SkipFunctor
> >>      takes any number of arguments; does completely nothing
> >>
> >> ReturnSomethingFunctor<T,t>
> >>      takes any number of arguments; returns t;
> >>
> >> IdentityFunctor
> >>      takes one parameter and returns it.
> >>
> >> ReturnFalseFunctor
> >>      takes any number of arguments; returns false;
> >>
> >> ReturnTrueFunctor
> >>      takes any number of arguments; returns true;
> >>
> >> ReturnZeroFunctor
> >>      takes any number of arguments; returns 0;
> >>
> >> AssertFunctor
> >>      takes any number of arguments; asserts;
> >>
> >> ArrayToFunctor<Array>
> >>      Stores an object which provides operator[].
> >>      Provides operator()().
> >>
> >> A set of non-template comparison functors (only operator() is
> templated):
> >>    * Greater
> >>    * Less
> >>    * GreaterEqual
> >>    * LessEqual
> >>    * EqualTo
> >>    * NotEqualTo
> >>
> >>
> >> FunctorToComparator<Functor, Compare>
> >>      This comparator  takes a functor "f" and a comparator "c".
> >>      For elements (x,y) it returns c(f(x), f(y))
> >>      c is Less by default
> >>
> >>
> >> FunctorToOutputIterator<**Functor>
> >>      The output iterator stores a functor and
> >>      each time the operator= is called the given functor is called
> >>
> >> Logical operators as functors:
> >>      * Not
> >>      * Or
> >>      * And
> >>      * Xor
> >>
> >> LiftBinaryOperatorFunctor<**Operator, FunctorLeft, FunctorRight>
> >>      Functor stores a binary operator "o" and two functors "f" and "g".
> >>      For given arguments args returns o(f(args), g(args)).
> >>
> >> Boolean functor adapters. Each of them stores a boolean functor
> >> and performs an appropriate logical operation in the operator().
> >>
> >>      * NotFunctor<Functor>
> >>      * OrFunctor<FunctorLeft, FunctorRight>
> >>      * AndFunctor<FunctorLeft, FunctorRight>
> >>      * XorFunctor<FunctorLeft, FunctorRight>
> >>
> >
> > Are you aware of Boost.Phoenix ( or its predecessor Boost.Lambda ) ? Also
> > some of the functors appear to duplicate functors in the C++ standard
> > library in functional.
> >
> > Logical Xor ?
> >
> > New and useful functors are always welcome but please look at Phoenix
> > first. If you feel you still have new functors maybe you can talk to the
> > Phoenix developers to see if they will fit in Phoenix, or submit your
> > library if there is enough interest by others.
> >
> >
> >
> >
> >> Regards,
> >>
> >> Piotr
> >>
> >> Hi Piotr,
>
> Like Edward suggested, Boost.Phoenix is your library for these kinds of
> things and much more.
>
> I had some fun rewriting your examples with Boost.Phoenix, please see the
> attached file.
>
> I omitted two cases: SkipFunctor and AssertFunctor. I'm not sure how to do
> that, nor do I see a potential use case for those ;-)
>
> Regards,
> Kris
>
>
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