New subject: [Boost-users] [boost] [Fit] formal review starts today

8 Mar 2016

      On Monday, March 7, 2016 at 2:52:09 AM UTC-6, Edward Diener wrote:
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On 3/7/2016 12:15 AM, Paul Fultz II wrote:
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On Sunday, March 6, 2016 at 9:42:19 PM UTC-6, Edward Diener wrote:
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On 3/3/2016 6:43 AM, Vicente J. Botet Escriba wrote:
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Dear Boost community, sorry for the late anounce
The formal review of Paul Fultz II's Fit library starts today, 2nd
March
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and ends on 13th March.
Fit is a header-only C++11/C++14 library that provides utilities for 
functions and function objects.
These are some comments/queries about the Fit documentation.
Introduction
The introduction says that Fit "provides utilities for functions and 
function objects." But it seems as if Fit works only with lambda 
functions and function objects.
Fit works with any generalized Callable:
http://en.cppreference.com/w/cpp/concept/Callable
Please document this. A generalized Callable is a much bigger set of 
functionality than just lambda functions and function objects.
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The term 'function' normally encompasses 
a much larger definition in C++ which includes global functions, static 
functions, member functions, and lambda functions.
Which is what Callable encompasses, but I used "function" since more 
people are familiar with that than Callable.
A 'function' and a Callable in C++ are two entirely different things. 
Use the one that is precise and don't worry what people are familiar 
with. Explain what a Callable is early on ( I know you explain it later 
) if you feel that people do not know what it means.
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Fit needs to be more 
precise in what it says it works with. It repeatedly refers to function 
objects and lambda functions as 'functions'. I think this vagueness of 
terminality is really confusing in the documentation.
Perhaps, I should refer to the Callable concept early on then.
See above.
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Quick Start:Function Objects
"We can make it behave like a regular function if we construct the
class
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as a global variable."
What about a non-global
sum_f sum = sum_f();
makes 'sum' not behave like a regular function other than the fact that 
the variable 'sum' may eventually go out of scope ?
In C++, a regular function is always global, there is no such thing as 
local 
function(sans gcc extensions).
My point is that the non-global 'sum' in my example above behaves just 
as much like a regular function as your global 'sum'. You may want to 
promote the idea of global function objects but I think that this is 
personally a bad idea. IMO global variables of any kind are to be avoided.
It is quite common in several modern C++ libraries to declare functions as
global objects. There are many advantages to this. Why do you believe it
should be avoided? Especially since it has the same effect as a free 
function.
DO you believe free function should be avoided as well?
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Quick Start:Lambdas
Why do we need both BOOST_FIT_STATIC_LAMBDA and 
BOOST_FIT_STATIC_LAMBDA_FUNCTION ? I would seem that 
BOOST_FIT_STATIC_LAMBDA_FUNCTION would be adequate and 
BOOST_FIT_STATIC_LAMBDA is just redundant, mimicking lambda syntax to
no
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purpose.
BOOST_FIT_STATIC_LAMBDA_FUNCTION and BOOST_FIT_STATIC_FUNCTION both 
define a 
function at global scope, and can only be used at global scope, whereas 
BOOST_FIT_STATIC_LAMBDA can be used to constexpr initialize local 
variables 
as 
well.
It might be good to add that when the end-user first encounters 
BOOST_FIT_STATIC_LAMBDA, because the name does not suggest 
initialization of local objects. Furthermore I cannot imagine why one 
would want to use it to initialize a local object,
Really? You just said that you would prefer avoiding global functions.
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so you might want to 
explain the benefit of doing so as opposed to the normal syntax for 
creating a lambda function.
Maybe the quick start guide isn't the place for this in the first place.
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In fact, BOOST_FIT_LIFT uses this since it is not always clear what 
context the user might call BOOST_FIT_LIFT.
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Quick Start:Overloading
The overloading adaptors show two or more lambda functions. Can they 
also work with function objects ? Or a mix of lambda functions and 
function objects ? In fact all the reamining Quick Start topics show 
examples with lambda functions. Do they also work with function objects
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Yes it can be used with function objects. I probably should show an 
example 
of 
that as well. I used the lambdas because of the terseness of them.
Evidently the adaptors can be used with any Callable. I think you should 
make that point very strongly and show that in examples also.
Agreed.
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Quick Start:Variadic
I do not understand what 'We can also make this print function
varidiac,
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so it prints every argument passed into it.' means ?
I'll try to explain that better, but basically it will print each 
argument, 
so:
print("hello", 5); // Will print "hello" and 5
I wouldn't associate that with the word 'Variadic' but I do think you 
need to explain that more clearly.
I always understood variadic to mean taking a variable number of 
arguments. What do you understand variadic to mean?
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I do not think the Quick Start explains very much since it is dealing 
with adaptors of which we know almost nothing and the explanation for 
these adaptors and what they actually do is very terse.
Probably can expand the explanation of adaptors a little more.
Good idea. What do adaptors create ?
They create a function.
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Different function objects I would 
imagine ? In that case how about the explanation that adaptors take 
Callables as input and generate function object types that adapt the 
original functionality of one or more Callables to some other purpose.
The examples are already show taking Callables. Are you suggesting I 
show an example taking a member function or something?
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In the 'Signatures' section of the Overview I read:
"All the functions are global function objects except where an explicit 
template parameter is required." I honestly don't know what this is 
supposed to mean. Does this refer to when function objects are referred 
to as parameters to the adaptors, functions, and utilities of the
library
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?
I don't understand what you are asking. It means that the function is 
written 
like this in the documentation:
template<class IntegralConstant> 
constexpr auto if_(IntegralConstant);
But its actually a function object like this in the code:
struct if_f 
{ 
     template<class IntegralConstant> 
     constexpr auto operator()(IntegralConstant) const; 
}; 
const constexpr if_f if_ = {};
However, `if_c` is written like this in the documentation:
template 
constexpr auto if_c(F);
It requires the bool `B` template parameter explicity. So in the code it 
is 
written as a function and not as a function object.
I don't understand to what you are referring when you say 'function'. 
Are you talking about adaptors in your library, functions in your 
library, or what ?
I am talking about all functions that are defined in the library, that
includes adaptors as well. I am not sure how to make that clearer.
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Please try to understand that your use of the word 
'function' is very broad but that the word 'function' in C++ has a much 
narrower meaning.
By function, I mean something like in the example:

template<class IntegralConstant>
constexpr auto if_(IntegralConstant);

I think everyone agrees that is a function in C++.

Re: [Boost-users] [boost] [Fit] formal review starts today

Paul Fultz II

Edward Diener

paul Fultz

Gavin Lambert

paul Fultz

Vicente J. Botet Escriba

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