Re: [boost] [review][Fit] Review of Fit starts today : September 8 - September 17

Subject: Re: [boost] [review][Fit] Review of Fit starts today : September 8 - September 17
From: P F (pfultz2_at_[hidden])
Date: 2017-09-16 23:53:44

> On Sep 16, 2017, at 2:31 PM, Edward Diener via Boost <boost_at_[hidden]> wrote:
> 
> On 9/16/2017 2:14 PM, P F via Boost wrote:
>> 
>>> 5) I do not understand the purpose of the pipable adaptor. What is the point of using it ? It is mentioned as an alternative to Unified Call Syntax but, while I understand the latter, I do not understandable how pipable allows "extension methods", which is a large part of the purpose of UFCS.
>> That is, you want to add an extension method to a class so it can be called as `x.f(y)`. With UFCS, you can just declare a free function called as `f(x, y)` and then call it as `x.f(y)`, with the Fit library you would declare the function as pipable and then call it as `x | f(y)`.
> 
> Let us suppose I have a class:
> 
> struct X { some member functions etc. };
> 
> Then I want to add a member function to class X with a prototype called void f(int) so I can call it as an extension method without modifying X. With UFCS in effect I create the free function:
> 
> void f(X px,int py) { some implementation }
> 
> and now if I have:
> 
> X x;
> 
> I can call:
> 
> x.f(3); // Works with UFCS support
> 
> successfully. Could you please show me the equivalent code that uses pipable in this same scenario ?

You could define `f` like this(using a lambda for simplification):

BOOST_FIT_STATIC_LAMBDA_FUNCTION(f) = boost::fit::pipable([](X px,int py) { some implementation });

And then you can call it like this:

X x;
x | f(3); // Calls f as f(x, 3)