Question

Can somebody explain me lambda expressions & what they can be used for. I have googled for it & have a rough idea. most of the examples give c# code. How about lambda expressions in plain old C…?

Answer 1

There are actually two things called “lambda expressions”, which are rather loosely related:

1. Lambda expressions are fundamental part of lambda calculus and are closely related to functional programming

2. In imperative languages, lambda expressions are usually synonyms for anonymous methods. In C#, for example you can pass lambda expression (ie. an expression itself, not just its result) as an argument:

C#:

someCollection.Apply (x => 2*x); // apply expression to every object in collection
// equivalent to 
someCollection.Apply (delegate (int x) { return 2 * X; });

Having said that, C does not support anonymous methods. You can, however, use function pointers to achieve similar results:

int multiply (int x)
{
    return 2 * x;
}

...
collection_apply (some_collection, multiply);