Scala: passing impure function to a HoF

Question

I came across a piece of scala code which makes use of map function in a very unexpected manner:

myList.map(item => someImpureFunction(item))

someImpureFunction has return type Unit.

Is it an acceptable way of doing FP?

score 4 · Accepted Answer · edited Aug 19 '21 at 11:19

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If someImpureFunction returns Unit it implies that the function performs some side effect e.g. writes to a database or standard output, so in that case, it's better to use:

myList.foreach(item => someImpureFunction(item))

If you want to write pure FP code you should take a look at deferring the execution of side effects (a good example is Cats IO)

edited Aug 19 '21 at 11:19

Gaël J

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answered Aug 19 '21 at 10:55

Bondarenko

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Or just `myList.foreach(someImpureFunction)` – Tim Aug 19 '21 at 11:24

Scala: passing impure function to a HoF

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