Add slices.Any, slices.None

[cloudshiftchris]

Any and None are useful constructs to determine if any (or none) of the elements match a predicate.

Sample implementations:

func Any[T any](ss []T, test func(T) bool) bool {
	for _, s := range ss {
		if test(s) {
			return true
		}
	}
	return false
}

func None[T any](ss []T, test func(T) bool) bool {
	for _, s := range ss {
		if test(s) {
			return false
		}
	}
	return true
}

[bobg]

Thank you for this suggestion.

As presented here, the functions seem too special-purpose to be in keeping with the other features of this module. A more general approach would allow you to, say, find the index of the first value that passes the test. It could return -1 if no such value is found. This allows the trivial implementation of Any and None and plenty of other functions besides.

func Any[T any](s []T, test func(T) bool) bool {
  return indexOf(s, test) >= 0
}

func None[T any](s []T, test func(T) bool) bool {
  return !Any(s, test)
}

func All[T any](s []T, test func(T) bool) bool {
  notTest := func(val T) bool { return !test(val) }
  return !Any(s, notTest)
}

As it happens, I am presently updating the go-generics module to align with the planned inclusion, in Go 1.21, of new slices and maps packages in the standard library. See golang/go#57433 and golang/go#57436. The idea is for my slices and maps to be drop-in replacements for the stdlib versions, with enhancements. And the stdlib slices package will include IndexFunc, which behaves in exactly the way I illustrated above with indexOf.

Sound OK?

[bobg]

(In fact, slices.ContainsFunc is exactly your Any.)

[cloudshiftchris]

Sounds good. Thanks for sharing the broader context.