Explain about closures in FP?

Question

Functional programming

Here, for example, is the Haskell code:
add a b = a + b
Everything seems to be fine, the function is clean. But you can also write it in another way, with blackjack closure and lambdas:
add = \a -> \b -> a + b
And here something becomes incomprehensible. It seems like both functions should be pure (after all, as far as I understand, in Haskell only functions of the IO () type or something like that can be "dirty", but here - the most ordinary functions). But at the same time, the lambda \b -> a + b, in theory, should not see the variable a. But she sees. Does that mean she's not clean?
Can you please explain how closures coexist with the functional paradigm?

Answer 1

Net. Consider foo = add 2, foo xfor some xalways returns the same value, and also does not produce any externally observable effect, and therefore falls under the definition of a pure function. Those. foo = add 2is identical to the function foo x = 2 + x, which is obviously pure.