gistfile1.txt

# .get example

class MapIterator does Iterator {
    has $.base-iterator;
    has $.code;
   
    multi method get() {
        my $value = $.base-iterator.get;
        $value ~~ Good ?? $.code($value) !! $value;
    }
}

# .next / .value example, .value invalid after .next returns false

class MapIterator does Iterator {
    has $.base-iterator;
    has $.code;

    multi method next() {
        $.base-iterator.next;
    }

    multi method value() {
        $.code($.base-iterator);
    }
}

# .next / .value example, .value "valid" after .next returns false

class MapIterator does Iterator {
    has $.base-iterator;
    has $.code;
    has $.current;

    multi method next() {
        my $okay = $.base-iterator.next;
        if ($okay) {
            $.current = $.code($.base_iterator.value);
        }
        else {
            $.current = $.base_iterator.value;
        }
    }

    multi method value() {
        $.current;
    }
}