86 lines
2.8 KiB
Perl
86 lines
2.8 KiB
Perl
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:- table direction_loop/1.
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:- op(700, xfx, l).
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:- op(700, xfx, r).
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From l To :- From to To-_.
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From r To :- From to _-To.
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% We want to satisfy {Offset_i + Stride_i*Loops_i + Sub_ij = Z}
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answer() :-
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starts(Starts),
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maplist([S, S-Off-Stride-Loop]>>(zloop([], S, 0, [], Off, Stride, Loop)),
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Starts, Events),
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maplist(split, Events, EquationSets),
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pick(EquationSets, Eqs),
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index1(Eqs, IEqs),
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write('Find N_i such that: '),
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foldl(write_eq, IEqs, _, _),
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write('Z\n'),
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% foldl(satisfy, EquationsN, _, Answer),
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true.
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write_eq(I-(A-B-C), _, _) :-
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writef('%t + %t*N%t ', [A, B, I]),
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(C =\= 0 -> writef('+ %t ', [C]); true),
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write('= ').
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% satisfy((A-B-C), N, Z, Z) :- natnum(N), Z is A + B*N + C.
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% [mma-2-2-[0-mmz], nna-3-6-[0-nnz, 3-nnz]] -> [2-2-0, 3-6-0, 3-6-3]
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split(_-_-_-[], []).
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split(A-Offset-Stride-[Sub-_ | Loop], [Offset-Stride-Sub | Cdr]) :-
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split(A-Offset-Stride-Loop, Cdr).
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% Everything above this is not needed to get the input answer
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% starts(Starts),
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% maplist([S, S-Off-Stride-Loop]>>(zloop([], S, 0, [], Off, Stride, Loop)),
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% Starts, Loops).
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% then find the LCD of the strides (which are equal to offsets).
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zloop(_, _, _, Zs, Offset, Stride, Loop) :-
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Zs = [FirstZIndex-Z | _], reverse(Zs, [LastZIndex-Z | ReversedZs]),
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DeltaZ is LastZIndex - FirstZIndex, DeltaZ =\= 0,
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direction_len(Len),
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divmod(DeltaZ, Len, _, 0),
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Offset = FirstZIndex, Stride = DeltaZ,
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foldl([Idx-Z, NewIdx-Z, Off, Off]>>(NewIdx is Idx - Off),
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ReversedZs, ReversedLoop, Offset, _),
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reverse(ReversedLoop, Loop),
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!.
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zloop(Directions, Node, Index, Zs, Offset, Stride, Loop) :-
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( is_end(Node)
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-> append(Zs, [Index-Node], NewZs)
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; NewZs = Zs
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),
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next_step(Directions, Move, Remain),
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G =.. [Move, Node, To], G,
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NewIndex is Index + 1,
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zloop(Remain, To, NewIndex, NewZs, Offset, Stride, Loop).
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starts(Starts) :- findall(X, X to _, Nodes), include(is_start, Nodes, Starts).
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is_start(Node) :- atom_chars(Node, [_, _, a]).
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is_end(Node) :- atom_chars(Node, [_, _, z]).
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next_step([Move | Remain], Move, Remain).
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next_step([], Move, Remain) :- direction_list([Move | Remain]).
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direction_list(Dir) :- direction(Str), atom_chars(Str, Dir).
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direction_len(Len) :- direction_list(D), length(D, Len).
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% pick([[1,2,3], [4], [5,6]], X). X = [1,4,5]; X = [1,4,6]; X = [2,4,5]; ...
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pick(ListOfLists, Items) :-
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maplist([SubList, X]>>(member(X, SubList)), ListOfLists, Items).
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index1(L, IL) :- reverse(L, RL), index1r(RL, IRL), reverse(IRL, IL).
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index1r([X], [1-X]).
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index1r([X, Y | Cdr], [NextI-X, I-Y | ICdr]) :-
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index1r([Y | Cdr], [I-Y | ICdr]), NextI is I + 1.
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same_elements([_]).
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same_elements([X-_, Y-Z2 | Cdr]) :- X =:= Y, same_elements([Y-Z2 | Cdr]).
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natnum(0).
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natnum(N) :- natnum(N0), N is N0 + 1.
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