Replace List.fold_left (||) false (List.map f lst) with List.exists f lst

[last-genius]

It's an equivalent, but much cleaner construct, which in addition avoids needlessly iterating over the list after the first match is found.

[changlei-li]

Should consider if f has side effect.

[changlei-li]

List.fold_left (||) false (List.map f lst) indeed will iterate the entire list as this PR says.
Another interesting finding is that List.fold_left (fun acc x -> acc || (f x)) false lst will also do short-circuit. When acc becomes true, the expression acc || (f x) doesn't evaluate (f x) due to OCaml's evaluation of ||. So the fold effectively stops calling f once the accumulator becomes true.