hg.stevelosh.com > temperance

test/99.pl @ 8cd3257c58e3 

Name the subterm-handling instructions something not completely stupid

The `unify-*` instructions in the original WAM are used both in both program
mode and query mode.  In program mode, they are used to unify subterms of
arguments with things.  In query mode, they are used to write the subterms of
the arguments into the head.

You may have noticed the common word in both of these descriptions is "subterm"
and not "unify".  Let's use that word to name the instructions so it's less
confusing.
author Steve Losh <steve@stevelosh.com>
date Sun, 10 Jul 2016 14:28:48 +0000
parents 5e0cca5174a8
children 4abb7eda96cb 
% 99 Prolog Problems
% from http://www.ic.unicamp.br/~meidanis/courses/mc336/2009s2/prolog/problemas/
%
% Solutions to at least a few of these, for testing purposes.

% P01
my_last(X, [X]).
my_last(X, [_ | T]) :-
    my_last(X, T).

% P02
my_lastbutone(X, [X, _]).
my_lastbutone(X, [_ | T]) :-
    my_lastbutone(X, T).

% P03
my_nth(X, [X | _], 1).
my_nth(X, [_ | T], N) :-
    M is N - 1,
    my_nth(X, T, M).

% P04
my_len([], 0).
my_len([_ | T], Length) :-
    my_len(T, M),
    Length is M + 1.

my_len_acc([], A, A).
my_len_acc([_ | T], A, Length) :-
    B is A + 1,
    my_len_acc(T, B, Length).

my_len2(L, Length) :-
    my_len_acc(L, 0, Length).

% P05
my_reverse_acc([], Acc, Acc).
my_reverse_acc([X | T], Acc, Reversed) :-
    my_reverse_acc(T, [X | Acc], Reversed).

my_reverse(L, R) :-
    my_reverse_acc(L, [], R).

% P06
my_palindrome(L) :-
    my_reverse(L, L).

% P07
my_flatten([], []).

my_flatten([Atom | Tail], [Atom | FlatTail]) :-
    \+ is_list(Atom),
    my_flatten(Tail, FlatTail).

my_flatten([HeadList | Tail], Flattened) :-
    is_list(HeadList),
    my_flatten(HeadList, FlatHeadList),
    my_flatten(Tail, FlatTail),
    append(FlatHeadList, FlatTail, Flattened).

% P08
my_compress_acc([], A, A).

my_compress_acc([X | T], [X | Acc], Compressed) :-
    my_compress_acc(T, [X | Acc], Compressed).

my_compress_acc([X | T], [Y | Acc], Compressed) :-
    X \= Y,
    my_compress_acc(T, [X, Y | Acc], Compressed).

my_compress([H | T], Compressed) :-
    my_compress_acc(T, [H], ReverseCompressed),
    my_reverse(ReverseCompressed, Compressed).

their_compress([],[]).
their_compress([X],[X]).
their_compress([X,X|Xs],Zs) :- compress([X|Xs],Zs).
their_compress([X,Y|Ys],[X|Zs]) :- X \= Y, compress([Y|Ys],Zs).

% P09
my_pack([], []).
my_pack([X], [[X]]).

my_pack([X | Tail], [[X] | ResultTail]) :-
    my_pack(Tail, ResultTail),
    ResultTail = [[Y | _] | _],
    X \= Y.

my_pack([X | Tail], [[X, X | XS] | ResultTail]) :-
    my_pack(Tail, [[X | XS] | ResultTail]).

their_pack([],[]).
their_pack([X | Tail], [Chunk | PackedTail]) :-
    their_transfer(X, [X | Tail], Remaining, Chunk),
    their_pack(Remaining, PackedTail).

% transfer(X,Xs,Ys,Z) Ys is the list that remains from the list Xs
%    when all leading copies of X are removed and transfered to Z

their_transfer(_, [], [], []).

their_transfer(X, [Y | Ys], [Y | Ys], []) :-
    X \= Y.

their_transfer(X, [X | Xs], Ys, [X | Zs]) :-
    their_transfer(X, Xs, Ys, Zs).