56 lines
1.5 KiB
Prolog
56 lines
1.5 KiB
Prolog
:- use_module(library(dcg/basics)).
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:- use_module(library(ugraphs)).
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:- use_module(library(assoc)).
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char(X, L, C0, L, C) -->
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[X0], {X0 \= 0'\n, char_code(X, X0), C is C0 + 1}, !.
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newline(L0, _, L, 0) --> "\n", {L is L0 + 1}.
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empty(L, C0, L, C) --> char('.', L, C0, L, C).
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pipe(Ds, L, C0, L, C) --> char(X, L, C0, L, C), {is_pipe(X, Ds)}.
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start(L, C0, L, C) --> char('S', L, C0, L, C).
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is_pipe('F', [down, right]).
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is_pipe('L', [up, right]).
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is_pipe('7', [down, left]).
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is_pipe('J', [up, left]).
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is_pipe('-', [left, right]).
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is_pipe('|', [up, down]).
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nonthing(L0, C0, L, C) --> empty(L0, C0, L, C).
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nonthing(L0, C0, L, C) --> newline(L0, C0, L, C).
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thing(s(L0, C0), L0, C0, L, C) --> start(L0, C0, L, C).
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thing(p(P, L0, C0), L0, C0, L, C) --> pipe(P, L0, C0, L, C).
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map([], L, C, L, C) --> [].
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map(Xs, L0, C0, L, C) --> nonthing(L0, C0, L1, C1), map(Xs, L1, C1, L, C).
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map([X|Xs], L0, C0, L, C) --> thing(X, L0, C0, L1, C1), map(Xs, L1, C1, L, C).
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map(Xs) --> map(Xs, 0, 0, _, _).
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insert(s(L, C), A0, A) :- put_assoc(L-C, A0, s, A).
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insert(p(P, L, C), A0, A) :- put_assoc(L-C, A0, p(P), A).
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make_assoc(Map, A) :-
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empty_assoc(Start),
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foldl(insert, Map, Start, A).
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parse(File, A) :-
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phrase_from_file(map(Map), File), !,
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make_assoc(Map, A).
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converse(up, down).
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converse(down, up).
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converse(left, right).
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converse(right, left).
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compat(p(Ds1), p(Ds2)) :- member(D1, Ds1), member(D2, Ds2), converse(D1, D2), !.
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compat(s, p(_)).
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compat(p(_), s).
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% vim: set ft=prolog :
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