Data commit

Task/Amb/Picat/amb.picat

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+go ?=>
+  % select which version of amb/2 and joins/2 to test
+  member(Amb,[amb,amb2]),
+  member(Joins,[joins,join2]),
+  println([amb=Amb,joins=Joins]),
+  test_amb(amb,joins, Word1,Word2,Word3,Word4),
+  println([Word1, Word2, Word3, Word4]),
+  nl,
+  fail, % get other solutions
+  nl.
+go => true.
+
+% Test a combination of amb and joins
+test_amb(Amb,Joins, Word1,Word2,Word3,Word4) =>
+  call(Amb, Word1, ["the","that","a"]),
+  call(Amb, Word2, ["frog","elephant","thing"]),
+  call(Amb, Word3, ["walked","treaded","grows"]),
+  call(Amb, Word4, ["slowly","quickly"]),
+  call(Joins, Word1, Word2),
+  call(Joins, Word2, Word3),
+  call(Joins, Word3, Word4).
+
+% Based on the Prolog solution.
+amb(E, [E|_]).
+amb(E, [_|ES]) :- amb(E, ES).
+
+joins(Left, Right) =>
+  append(_, [T], Left),
+  append([R], _, Right),
+  ( T != R -> amb(_, [])
+  ; true ).
+
+% Another approach, using member/2 for
+% generating the words.
+amb2([],[]).
+amb2(Word,Words) :- member(Word,Words).
+
+joins2(Word1,Word2) :- Word1.last() = Word2.first().