: >string-index
    "" split
    "&'0123456789abcdefghijklmnopqrstuvwxyz" "" split
    swap index collapse ;
: chars  "" split length swap drop ;
: cr  "\n" . ;
: nip  swap drop ;
: ordered?
    dup grade subscript != '+ reduce if 0 else -1 then ;

: filtering
    [] '_ set
    0 do read
        2dup chars
        <=
        if  dup >string-index ordered?
            if   2dup chars
                 <
                 if   nip dup chars swap
                      [] '_ set
                 then
                 _ swap append '_ set
                 '. .                       # progress dot
            else drop
            then
        else drop
        then
    eof if break then loop

    cr _ . cr
    ;

: ordered-words
    '< 'unixdict.txt open 'fh set
    fh fin filtering fh close ;

ordered-words