Tell me which option is correct? Are functions sup...

# functional

[Vitaliy Zarubin]

Tell me which option is correct? Are functions supposed to run from right to left?

[Vitaliy Zarubin]

Or does it not matter and depends on the task?

[Roukanken]

in math, function composition works like this: (f ◌ g)(x) = f(g(x))
in Java, the Function<A, B> interface has 2 functions, compose that works like mathematical one
and andThen function that works the other way around, eg:
a.compose(b).apply(x) = a.apply(b.apply(x))
a.andThen(b).apply(x) = b.apply(a.apply(x))
(apply is Functions's invoke )

From what I seen, usually programmers prefer to use andThen as they consider it more intuitive to work with it. (As when you are writing, you usually want to apply functions in order you are writing them)

So yeah, answer is - it depends. But don't forget to name it properly - eg, the first one is andThen but other should be called composition or some similar names...

[Vitaliy Zarubin]

Found about it.
https://twitter.github.io/scala_school/pattern-matching-and-functional-composition.html