TakeIgnoreSeq.pm6

#use MONKEY-TYPING;

class TakeIgnoreIterator does Iterator {
    has Seq         $.original-seq;
    has Iterator    $!original;
    has Iterator    $.handling;
    has Iterator    $!not-handled;
    has             $.condition = {True};
    has Bool        $.taking    = False;
    method pull-one {
        my $response;
        with $!original-seq {
            $!original      = $!original-seq.iterator;
            $!original-seq  = Nil
        }
        with $!original {
            if $!original !~~ ::?CLASS {
                $!handling = $!original;
                $!original = Nil
            } else {
                $response := .pull-one;
                if $response =:= IterationEnd {
                    with $!original.not-handled {
                        $!handling = $_
                    }
                }
            }
        }
        with $!handling {
            $response := .pull-one;
            if $!taking {
                unless $response !=:= IterationEnd and $response ~~ $!condition {
                    $!not-handled = $!handling;
                    $!handling = Nil;
                    $response := IterationEnd
                }
            } else {
                until $response =:= IterationEnd {
                    last unless $response ~~ $!condition;
                    $response := .pull-one;
                }
                $!not-handled = $!handling;
                $!handling = Nil;
                $response := IterationEnd
            }
        }
        return $response
    }
    method not-handled {
        with $!not-handled {
            my $nh = $!not-handled;
            $!not-handled = Nil;
            return $nh
        }
    }
}
role TakeIgnoreSeq[$parent = Nil] {
    has Seq $.ignored = $parent;
    method take-while($condition, Seq :$ignored) {
        return .take-while: $condition with $!ignored;
        Seq.new(TakeIgnoreIterator.new: :original-seq(self), :$condition, :taking) but TakeIgnoreSeq[$ignored];
    }
    method take-until($condition, Seq :$ignored) {
        return .take-until: $condition with $!ignored;
        Seq.new(TakeIgnoreIterator.new: :original-seq(self), :condition{ $_ !~~ $condition }, :taking) but TakeIgnoreSeq[$ignored];
    }
    method ignore-while($condition) {
        my $ignored = Seq.new(TakeIgnoreIterator.new: :original-seq(self), :$condition, :!taking) but TakeIgnoreSeq;
        $ignored.take-while(True, :$ignored)
    }
    method ignore-until($condition) {
        my $ignored = Seq.new(TakeIgnoreIterator.new: :original-seq(self), :condition{ $_ !~~ $condition }, :!taking) but TakeIgnoreSeq;
        $ignored.take-while(True, :$ignored)
    }
}

#augment class Seq { method TWEAK (|) { self does TakeIgnoreSeq } }