1% Define character classes
    2:- module(tidylog_char, [ horizontal//0
    3                        , nl//0
    4                        , invisible//0
    5                        ]).

 horizontal//

Matches a single horizontal character (space or tab). It prefers a space character.

   12horizontal -->
   13    " ".
   14horizontal -->
   15    "\t".

 invisible//

Matches a single non-visible (whitespace) character. It prefers a newline.

   22invisible -->
   23    nl.
   24invisible -->
   25    horizontal.

 nl//

Matches a single newline character.

   31nl -->
   32    "\n"