
mem_dl  mem_dl is true when it's first argument is
a member of the second argument. The second argument is constrained to
be a difference list. This predicate should have an open signature,
i.e. it will accept 0 of its arguments as being grounded. This predicate
may produce redundant solutions.
? mem_dl(t, [a, b, c, d, t, g, h][d, t, g, h]).
No.
? mem_dl(a, [a, b, c, d, t, g, h][d, t, g, h]).
Yes.
? mem_dl(X, [a,b,c][]).
X = a ;
X = b ;
X = c ;
No.
? mem_dl(a, X).
X = [a_G1]_G1 ;
X = [_G1,a_G2]_G2 .
Yes.

empty_dl  empty_dl is true when the argument given
to it is a difference list, which is empty. This should accept the
signatures: empty_dl(+), or empty_dl().
? empty_dl([][]).
Yes.
? empty_dl([a,b,c][a,b,c]).
Yes.
? empty_dl([a,b,c][b,c]).
No.

equal  equal is true when the two lists given to it
as arguments are equivalent, this predicate should work on either difference
lists or normal lists. This predicate should accept the signatures:
equal(+,), equal(,+), equal(+,+).
? equal([][],[][]).
Yes.
? equal([a,b][b],[a,b][]).
No.
? equal([c, d][d],[c,d][d]).
Yes.
? equal([],[][]).
Yes.
? equal([a], [a,b,c,d,e,f][b,c,d,e,f]).
Yes.
? equal([a], [a,b,c,d,e,f][c,d,e,f]).
No.

length_dl  length_dl is true when the second argument,
which should be a number, is equal to the number of elements in the difference
list that is the first argument. This should accept any of the signatures:
length_dl(+,), length_dl(,+), or length_dl(+,+).
? length_dl([a,b,c,d,e,f][e,f], X).
X = 4 ;
No.
? length_dl([a,b][],X).
X = 2 ;
No.
? length_dl([][], X).
X = 0 .
Yes.
? length_dl(X, 3).
X = [_G1,_G2,_G3G4]G4 .
Yes.

samelen_dl  samelen_dl is true when the two difference
lists given to it are of the same length. This predicate should accept the
signature samelen_dl(+,+).
? samelen_dl([a,b,c,d,e,f][d,e,f], [g,h,i,j,k,l,m][j,k,l,m]).
Yes.
? samelen_dl([a,b,c,d,e,f][e,f], [g,h,i,j,k][k]).
Yes.
? samelen_dl([a,b,c,d,e,f][e,f], [a,b,c,d,e,f][e,f]).
Yes.
? samelen_dl([a,b,c,d,e,f][e,f], [a,b,c,d,e,f][c,d,e,f]).
No.

samelen  samelen is true when the two lists given to
it as arguments have the same length. It should be able to take either
difference lists or normal lists. This predicate need only
accept the signature samelen(+,+).
? samelen([a,b,c,d,e,f][d,e,f],[a,b,c,d,e,f,g][d,e,f,g]).
Yes.
? samelen([a,b,c,d,e,f][d,e,f],[t,y,z]).
Yes.
? samelen([a,b,c,d,e,f][d,e,f], [a,b,c,d,e,f][c,d,e,f]).
No.
? samelen([a,b,c,d,e,f],[w,x,y,z,q,r]).
Yes.
? samelen([a,b,c,d,e,f], [w,x,y,z]).
No.
? samelen([a,b,c,d],[a,b,c,d][d]).
No.
? samelen([], [a,b,cX][a,b,cX]).
Yes.
Your file should contain ALL functions necessary for the assignment, do
not run the script several times to hand in different portions of the assignments.
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