USING: kernel sequences splitting ;

: remove-.. ( seq -- newseq )
    dup empty?
    [ unclip dup ".." =
      [
          drop dup empty? [ drop { ".." } ] [ rest remove-.. ] if
      ]
      [
          [ remove-.. ] dip prefix
      ]	if
    ] unless ;

: simplify ( path -- newpath )
    "/" split reverse
    remove-.. reverse "/" join ;