Documentation

Check that if predicate holds for any inputs to the fold.

>>> run [1, 2, 3, 4] (any even)
True

>>> run [] (any $ const False)
False

Check that if predicate holds for all inputs to the fold.

>>> run [1, 2, 3, 4] (all (< 6))
True

>>> run [1, 2, 3, 4] (all (> 1))
False

Check whether all elements are True.

>>> run (repeat False) and
False

>>> run (repeat True) and
... diverges ...

Check whether any elements are True.

>>> run (True : repeat False) or
True
>>> run (repeat False) or
... diverges ...

Find the first element for which a predicate holds.

>>> run [1, 2, 3, 4] (find even)
Just 2

>>> run [1, 2, 3, 4] (find (> 4))
Nothing

Find the first index for which a predicate holds.

>>> run [1, 2, 3, 4] (indexOf (== 4))
Just 3

>>> run [1, 2, 3, 4] (indexOf (> 4))
Nothing

Grab the first inputted element.

>>> run [1 ..] head
Just 1

>>> run [] head
Nothing

Occasionally we want to use a short-circuiting fold with other, nonlazy folds. This function drops laziness on the floor for a L' fold. This is dangerous because it can potentially effect termination behavior.

>>> run (repeat False) and
False

>>> run (repeat False) (strictify and)
... diverges ...

This means it is only advisable to use when combining a monoidal fold with something that requires left folding.

>>> run [1.0, 2, 3, 4] $ (/) <$> strictify head <*> maximum
0.25