How does Array.Extra.all short circuit?

rupert · February 16, 2023, 8:15pm

elm-community/array-extra/blob/2.6.0/src/Array/Extra.elm#L707


      
              fromList [ 4, 16 ] |> all (\x -> x < 5)
              --> False
          
          
    empty |> all (\x -> x < 5)
              --> True
          
          
-}
          all : (element -> Bool) -> (Array element -> Bool)
          all isOkay =
              Array.foldl
                  (\element soFar -> soFar && isOkay element)
                  True
          
          

          
{-| Whether at least some elements satisfy a given test.
          
          
    import Array exposing (fromList, empty)
          
          
    fromList [ 6, 3 ] |> any (\x -> x < 5)
              --> True

I think the accumulator soFar becomes False and then the expression soFar && isOkay element never evaluates the isOkay element bit sionce && short circuits. But it will still loop over the entire array, all the way to the end.

You could experiement by changing the all code to:

all : (element -> Bool) -> (Array element -> Bool)
all isOkay =
    Array.foldl
        (\element soFar -> isOkay element && soFar)
        True

Then running that through your Ellie.

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How does Array.Extra.all short circuit?

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