CODEWITHSUNDEEP
c++boostmacrositeratorboost-iterators
superspacemarines
superspacemarines

Reputation: 211

C++ BOOST ForEach vs custom defined Macro

What is the Difference between using BOOST's ForEach and my own custom #define macro to iterate through a container??

mine:

#define iterate(i,x)     for(typeof(x.begin()) i=x.begin();i!=x.end();++i)

boost:
#include <string>
#include <iostream>
#include <boost/foreach.hpp>

int main()
{
    std::string hello( "Hello, world!" );

    BOOST_FOREACH( char ch, hello )
    {
        std::cout << ch;
    }

    return 0;
}

Please explain which method is better and why?

Upvotes: 2

Views: 957

Answers (1)

Paul Fultz II
Paul Fultz II

Reputation: 18210

First big difference, is when you using rvalues, like this:

vector<int> foo();

// foo() is evaluated once
BOOST_FOREACH(int i, foo())
{

}

// this is evaluated twice(once for foo().begin() and another foo().end())
iterate(i, foo())
{

}

This is because BOOST_FOREACH detects if it is an rvalue and makes a copy(which can be elided by the compiler).

The second difference is BOOST_FOREACH uses Boost.Range to retrieve the iterators. This allows it to be extended easily. So it will work on arrays and std::pair.

The third difference, is your iterate macro automatically deduces the type of the range, which can be very convenient on older compilers that support typeof but not auto. However, BOOST_FOREACH will work on all C++03 compilers.

Upvotes: 2

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