function filter(predicate) {
    return flatMap(value => predicate(value) ? maybe_1.just(value) : maybe_1.nothing());
}
function filter(predicate) {
    return flatMap(value => predicate(value) ? maybe_1.just(value) : maybe_1.nothing());
}
function filter ( predicate ) { return flatMap ( value => predicate ( value ) ? maybe_1 . just ( value ) : maybe_1 . nothing ( ) ) ; }
Return the current maybe if it has a value that matches the predicate, else return an empty
Return the current maybe if it has a value that matches the predicate else return an empty