Re: Adding optional<T&> find like method to associative containers in boost.

From: Peter Dimov (pdimov_at_[hidden])
Date: 2024-12-21 13:32:52

Andrey Semashev wrote:
> On 12/21/24 15:11, Peter Dimov via Boost wrote:
> > Christian Mazakas wrote:
> > What this user has always wanted is to not have to write this:
> >
> >   auto it = map.find( key );
> >   if( it != map.end() )
> >   {
> >     // do something with it->second
> >   }
> >
> > That's why I'm always defining a helper function `lookup` that returns
> > a pointer, which allows me to write this instead:
> >
> >   if( auto p = lookup( map, key ) )
> >   {
> >     // do something with *p
> >   }
> 
> I'll note that with C++17 you can also write this:
> 
>   if ( auto it = map.find( key ); it != map.end() )
>   {
>     // do something with it->second
>   }
> 
> But each of the three variants seem pretty much equivalent to me, from the
> code clarity standpoint.

It was admittedly much worse in C++03, where you had to spell out

std::map<key_type, mapped_type>::const_iterator it

in its entirety. Plus a typename in front if you happened to be in a template.

C++17 makes it almost palatable, except for the need to repeat `it->second`.