Re: [Boost-users] [Fit] upcoming formal review for Boost.Fit

Subject: Re: [Boost-users] [Fit] upcoming formal review for Boost.Fit
From: Vicente J. Botet Escriba (vicente.botet_at_[hidden])
Date: 2016-02-28 08:15:03

Le 27/02/2016 17:41, Steven Watanabe a écrit :
> AMDG
>
> On 02/27/2016 09:16 AM, Vicente J. Botet Escriba wrote:
>> The formal review of Paul Fultz II's Fit library starts on Wednesday,
>> 2nd March and ends on 13th March.
>>
>> Fit is a header-only C++11/C++14 library that provides utilities for
>> functions and function objects.
>>
> constexpr infix_adaptor<plus_f> plus = {};
> int r = 3 <plus> 2;
>
>    This is clever idea, but I'd really like to
> see an analysis of how it interacts with
> operator precedence.
>
>
You should consider the normal precedence for operator<() and 
operator>() and use parenthesis when you are not sure what will be the 
result ;-) There is no magic.

Idealy I would like that we can use a different symbol to enclose the 
function name e.g;the back-quote  '`' which is not used now and have 
left associativity with the highest precedence, but this is not possible 
now and would very probably never be :(

I found it useful e.g. if you have a binary function

     mbind(Monad, Callable) -> Monad

Using the infix notation allows to chain the continuations in a more 
natural way

     m <mbind> []() {....}  <mbind> []() {....}

instead of

     mbind(mbind(m, []() {....}), []() {....} );

What is terrible is that the following (I believe) will work also :(

     m < mbind > []() {....}  < mbind > []() {....}

and also that :( :(

     ((m <   mbind)    > []() {....}  <   mbind)     > []() {....}

Of course we don't want to write code like this one, but ...

With the first proposal of uniform call syntax we were able to have 
something similar

     m.mbind(f).mbind.(g);

but this equivalence has not been retained for the time been.

So I could summarize the infix adaptor is just syntactic sugar that 
doesn't respond completlly to my final goal, and should be used sparsely.

Vicente

P.S. Paul, maybe you can add something about this in the documentation 
of infix.