What method should be used to perform a side-effect using the value of the left side of an `Either`?...

# arrow

[julian]

What method should be used to perform a side-effect using the value of the left side of an Either? I could use fold. But that doesn't seem quite right since fold `s intent seems to be more on producing a value, not performing side-effects.

[julian]

Guess I'm looking for something that takes (A) -> Unit.

[julian]

fun Either<A, B>.foo((A) -> Unit): Either<A, B>

[streetsofboston]

IIRC, There used to be functions on Either named tap and tapLeft, to model side-effects. A lot has changed, not sure if they are still there...

[julian]

Ah, yes. I remember seeing those before. You're right. That was what I was looking for.