Question

I want to check if two lists A and B are equal, i.e., a1 == b1, a2 == b2,…

I have a working solution:

all (\x->x) zipWith $ (==) A B

Another idea is to do it recursively: a:as, b:bs ; check if a1==b1 and call the function with the remaining lists as and bs. But isn’t there an easier and more readable way to do this?

Answer 1

You can just use == on them directly.

> [1, 2, 3] == [1, 2, 3]
True
> [1, 2, 3] == [1, 2]
False

This is because == is part of the Eq type class, and there is an Eq instance for lists which looks something like this:

instance Eq a => Eq [a]

This means that lists instantiate Eq as long as the element type also instantiates Eq, which is the case for all types defined in the standard Prelude except functions and IO actions.