Re: Iterators and functors

From:
John Harrison <john_andronicus@hotmail.com>
Newsgroups:
comp.lang.c++
Date:
Tue, 06 Mar 2007 21:41:54 GMT
Message-ID:
<CelHh.30163$mn2.5500@newsfe7-win.ntli.net>
tryptik@gmail.com wrote:

Hello all,

I have a question about iterators. I have a container of functors
that operate on an std::string. The functors go something like this:

class Functor {
   std::string operator()(const std::string& s) {/*manipulate
string*/; return newString;}


Functors should be const

    std::string operator()(const std::string& s) const
    {
        ...
    }

};

Now, I want to call the functors on a string argument. I write
something like this:

std::vector<Functor> vec;

/*Omitted creation and push_back of a couple Functors */

std::vector<Functor>::const_iterator it = vec.begin();
std::vector<Functor>::const_iterator end = vec.end();

std::string arg("Test argument");

for(; it != end; it++)
   std::cout << *it(arg) << "\n"; //Why doesn't this work?

Instead of using the de-reference operator '*', I have to write the
following:

   it->operator()(arg);

Can some kind soul explain to me why this is? I prefer the cleaner
syntax of the first statement.

-tryptik


Just a question of operator precedence I think, try this.

     std::cout << (*it)(arg) << "\n";

john

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