where method
Filters this Option
based on the given predicate
function.
Returns None if this Option
is None, otherwise calls predicate
with
the held value, returning:
See also:
Rust: Option::filter()
Implementation
Option<T> where(bool Function(T) predicate) => switch (this) {
Some(:T v) => predicate(v) ? this : None(),
None() => this
};