Jan Burse, created May 22. 2019
* Prolog text ptree from Chat80 as a module.
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* Obtained rights comment in Prolog text and text from LICENSE file:
* @(#)ptree.pl 24.1 2/24/88
* Copyright 1986, Fernando C.N. Pereira and David H.D. Warren,
* All Rights Reserved
* This program may be used, copied, altered or included in other programs
* only for academic purposes and provided that the authorship of the
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/* Print term as a tree */
% :- mode print_tree(+).
% :- mode pt(+,+).
% :- mode pl(+,+).
% :- mode as_is(+).
% :- mode simplify(+,?),