Mailinglist Archive: zypp-devel (149 mails)

[Michael Andres <ma@xxxxxxx>]

Hi!


   std::vector<RepoInfo> toModify;
   getRepositoriesInService(oldAlias,
     std::insert_iterator<std::vector<RepoInfo> >( toModify, toModify.begin() 
));


Reading such a line you know why some people complain about templates.

a) It's not readable.
b) It's not reasonable.



Usually there are also convenience methods that build the right 
object for you. For the purpose here STL provides:

  std::back_inserter(container&)
  std::front_inserter(container&)


Now the above can be written as:

  std::vector<RepoInfo> toModify;
  getRepositoriesInService( oldAlias, std::front_inserter(toModify) );



The benefit is IMO obvious. And now as we can read the code, we 
may recognize that we don't want to use a front_inserter with a 
vector. We don't want to shift the whole array to the right on each 
insert. We want this:

  getRepositoriesInService( oldAlias, std::back_inserter(toModify) );



or 
  getRepositoriesInService(oldAlias,
    std::insert_iterator<std::vector<RepoInfo> >( toModify, toModify.end() ));

Whenever you have to write such a beast, you should ask yourself whether 
it's not worth writing a short convenience method. You already wrote the 
body:

   insert_iterator<std::vector<RepoInfo> >( toModify, toModify.end() )


Just put it into a function with a resonable name:

   template<class Container>
   inline insert_iterator<Container>  back_inserter( Container & c )
   { return insert_iterator<Container>( c, c.end() ); }

-- 

cu,
    Michael Andres

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