Re: [boost] [review] Review of PolyCollection starts today (May 3rd)

6 May 2017

      On 5/6/2017 5:07 AM, Joaquin M López Muñoz via Boost wrote:
...
El 06/05/2017 a las 5:53, Edward Diener via Boost escribió:
...
On 5/2/2017 7:46 PM, Ion Gaztañaga via Boost wrote:
...
Hi everyone,
The formal review of Joaquín M. López Muñoz's PolyCollection library 
starts today.
[...]
* boost::function_collection
I could not understand from the documentation what it is I am supposed 
to be
inserting into a function_collection. The tutorial did not explain 
this to me and the
reference's technical explanation on this eluded me.
You can insert into a boost::function_collection<Signature> any entity 
that a
std::function<Signature> object could be constructed from. For instance,
boost::function_collection holds callable entities that can 
be invoked with
a (convertible to) int argument and return a (convertible to) double 
result:
double f(int n){return (double)n;}
struct g
   {
     double operator()(int n)const{return (double)2*n;}
   };
boost::function_collection c;
   c.insert(&f);
   c.insert(g{});
   double factor=3;
   c.insert([=](int n){return factor*n;});
for(const auto& x:c)std::cout<
This is explained in http://tinyurl.com/kddv9nz . Didn't you find this 
section
sufficiently explanatory?
The explanation you cite with the link above is a tutorial, not an 
explanation. Furthermore, perhaps for the sake of syntactical brevity, 
you cite an example in which a lambda function returns another lambda 
function !!! This may be exceedingly clever but it can hardly be a 
mainstream explanation of your functionality which most programmers 
would easily understand as how a function collection "works". Your 
examples above are a much better and more mainstream example of how the 
function_collection works, and even the short explanation you have given 
me should have been in the documentation.

It is also hard to understand what the advantage of a poly collection of 
these objects entail over a more normal C++ collection ( vector, array 
etc. ) of std::function<Signature> objects, since the latter object type 
already represents a generalized callable construct in C++. Some of your 
performance tests suggest there is little or no advantage, so a 
discussion of this would have been welcome in the documentation.
...
Joaquín M López Muñoz