sasa, Prolog - rextester

sasa

:- module('automata/printing',
          [regex_to_string/2,
           format_table/1
           ]).

:- meta_predicate
       regex_to_string(+, -),
       format_table(+).

/** <module> Predicates for pretty printing
This module defines predicates useful to print structures generated by
other automata modules.
@see    https://github.com/wvxvw/intro-to-automata-theory
*/

:- use_module('automata/ast').

vexp(rterminal(C))  --> { C = [], !, R = 603 ; char_code(C, R) }, [R].
vexp(runion(L, R))  --> "(", vexp(L), "+", vexp(R), ")".
vexp(rstar(E))      --> "(", vexp(E), ")*".
vexp(rconcat(L, R)) --> vexp(L), vexp(R).

%%  regex_to_string(+Exp, -Result) is det.
%
%   Evaluates to true when given regular expression Exp can be written
%   as Result string.
%
%   @see    regex/1

regex_to_string(Exp, Result) :-
    phrase(vexp(Exp), Codes), text_to_string(Codes, Result).

format_table_helper([]).
format_table_helper([row(N, Row) | Table]) :-
    format('~w | ~w |~n', [N, Row]),
    format_table_helper(Table).

%%  format_table(+Table:table) is det.
%
%   Pretty-prints the contents of the transitions table.
%
%   @see    nfa_to_dfa/2, nfa_table/2

format_table(table(Inputs, Table)) :-
    format('~w~n', [Inputs]),
    format_table_helper(Table).


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