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

16 Sep 2017

      On 9/16/2017 2:14 PM, P F via Boost wrote:
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On Sep 15, 2017, at 8:46 PM, Edward Diener via Boost  wrote:
On 9/8/2017 7:02 AM, Matt Calabrese via Boost wrote:
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A formal review of the Fit library developed by Paul Fultz II starts
today, September 8, and runs through September 17.
A branch has been made for the review. You can find Fit for review at
these links:
Source: https://github.com/pfultz2/Fit/tree/boost https://github.com/pfultz2/Fit/tree/boost
Docs: http://pfultz2.github.io/Fit/doc/html/doc/ http://pfultz2.github.io/Fit/doc/html/doc/
I have some questions about Fit which I can not understand by reading the docs:
1) Does Fit functionality work only with function objects as opposed to callables in general ?
In general yes, but its not the case for every adaptor.
OK.
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2) Is the purpose of BOOST_FIT_STATIC_FUNCTION only to create a function object at global or namespace level ?
Yes.
OK.
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3) Does BOOST_FIT_STATIC_FUNCTION only accept a function object or does it accept any callable ?
It only works with function objects, which I should document its type requirements.
Please do.
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4) The documentation says that "BOOST_FIT_STATIC_LAMBDA_FUNCTION can be used to the declare the lambda as a function". I am not sure what this actually means since a lambda function is a function.
Maybe that could be worded better, but it lets you declare the lambda at global or namespace scope.
OK.
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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 ?
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In general I am confused by what the requirements of Fit adaptors are.
Which ones?
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This may be because the terms "function objects" and "functions" are used in a way which does not follow standard C++ terminology as far as I know it.
The type requirements for the adaptors are documented as either `ConstCallable` or `ConstFunctionObject`, which follows standard C++ definitions with an additional `const` requirement.
OK.

Thanks !
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