Question

Today I was doing some catch-up on c++11 (as we have not moved on yet). One of the reasons to switch as stated by a lot of people seems to be lambda expressions. I am still unsure on how they offer something new.

For instance using c++11:

#include <iostream>

int main()
{
    auto func = [] () { std::cout << "Hello world" << std::endl; };

    func();
}

seems to be very similar to:

#include <iostream>

#define FUNC( )\
        do { std::cout << "Hello world" << std::endl; } while(0)


int main()
{
    FUNC();
}

What would lambda expressions offer me that I can’t currently already do?

Answer 1

http://msdn.microsoft.com/en-us/library/vstudio/dd293608.aspx sums up the main points and more on the subject in great detail. Here is the salient excerpt:

A lambda combines the benefits of function pointers and function
objects and avoids their disadvantages. Like a function objects, a
lambda is flexible and can maintain state, but unlike a function
object, its compact syntax doesn’t require a class definition. By
using lambdas, you can write code that’s less cumbersome and less
prone to errors than the code for an equivalent function object.

There are examples on the site showing more differences and comparisons.

Also…conventional wisdom is never use macros in C++:

http://scienceblogs.com/goodmath/2007/12/17/macros-why-theyre-evil/