Re: [Boost] [Lambda2] Review starts Monday March 22, 2021 to March 31, 2021

From: Gavin Lambert (boost_at_[hidden])
Date: 2021-03-22 06:48:43

On 22/03/2021 5:48 pm, Robert Ramey wrote:
> I have a really dumb question about this.  Consider the count_if 
> example.  I understand how example works.  But I can't figure out where 
> the parameter _1 gets filled in. So I think that the count_if example 
> should be completed with a small bit of code which uses the newly 
> count_if function.

The _1 parameter is filled in by std::count_if itself (in this case, 
using each element of the passed iterators).  That's the point of a 
lambda, so I'm not quite sure what you're unclear on.  This is not 
creating a "count_if" function, if that's what you thought; it is a 
complete example including both definition and usage.

Having said that, I do think the docs could benefit by having some 
"compare and contrast" examples -- i.e. showing how each of those 
examples would have been implemented using C++11 lambdas or std::bind 
instead (and thus demonstrate the syntactic benefits of the library).