tapLeft

inline fun tapLeft(f: (A) -> Unit): Either<A, B>

The given function is applied as a fire and forget effect if this is a Left. When applied the result is ignored and the original Either value is returned

Example:

import arrow.core.*

fun main() {
  Either.Right(12).tapLeft { println("flower") } // Result: Right(12)
  Either.Left(12).tapLeft { println("flower") }  // Result: prints "flower" and returns: Left(12)
}