Re: Iterators and functors

From:
"Jim Langston" <tazmaster@rocketmail.com>
Newsgroups:
comp.lang.c++
Date:
Wed, 7 Mar 2007 08:29:02 -0800
Message-ID:
<rLBHh.76$zr5.71@newsfe06.lga>
<tryptik@gmail.com> wrote in message
news:1173216043.525047.114890@q40g2000cwq.googlegroups.com...

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;}
};

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?


As stated by others, this is actually:
*(it(arg))
But what you really want is
(*it)(arg)
so you have to specify that.

I now always use (*it) when derefernecing iterators for any context.

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

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