“isDuped” predicate in Prolog
I am trying to create a predicate in prolog called isDuped( Y ) that only succeeds if Y is a list of even length and each element in the list appears twice in a row (i.e. [1,1,2,2,3,3,4,4]).
What I currently have is:
isDuped( Y ) :-
Y == .
isDuped( Y ) :-
[ A, B | C ] = Y,
A == B,
isDuped( C ).
However, one of my professor's unit tests is supposed to return true, but as I have it written it returns false. isDuped([1,_]) is supposed to return true, but I have no idea what I need to change. Any help would be appreciated.
prolog
asked Nov 24 '18 at 3:21
ScottyDScottyD
153
add a comment |
I am trying to create a predicate in prolog called isDuped( Y ) that only succeeds if Y is a list of even length and each element in the list appears twice in a row (i.e. [1,1,2,2,3,3,4,4]).
What I currently have is:
isDuped( Y ) :-
Y == .
isDuped( Y ) :-
[ A, B | C ] = Y,
A == B,
isDuped( C ).
However, one of my professor's unit tests is supposed to return true, but as I have it written it returns false. isDuped([1,_]) is supposed to return true, but I have no idea what I need to change. Any help would be appreciated.
prolog
asked Nov 24 '18 at 3:21
ScottyDScottyD
153
add a comment |
I am trying to create a predicate in prolog called isDuped( Y ) that only succeeds if Y is a list of even length and each element in the list appears twice in a row (i.e. [1,1,2,2,3,3,4,4]).
What I currently have is:
isDuped( Y ) :-
Y == .
isDuped( Y ) :-
[ A, B | C ] = Y,
A == B,
isDuped( C ).
However, one of my professor's unit tests is supposed to return true, but as I have it written it returns false. isDuped([1,_]) is supposed to return true, but I have no idea what I need to change. Any help would be appreciated.
prolog
asked Nov 24 '18 at 3:21
ScottyDScottyD
153
I am trying to create a predicate in prolog called isDuped( Y ) that only succeeds if Y is a list of even length and each element in the list appears twice in a row (i.e. [1,1,2,2,3,3,4,4]).
What I currently have is:
isDuped( Y ) :-
Y == .
isDuped( Y ) :-
[ A, B | C ] = Y,
A == B,
isDuped( C ).
However, one of my professor's unit tests is supposed to return true, but as I have it written it returns false. isDuped([1,_]) is supposed to return true, but I have no idea what I need to change. Any help would be appreciated.
prolog
prolog
asked Nov 24 '18 at 3:21
ScottyDScottyD
153
asked Nov 24 '18 at 3:21
ScottyDScottyD
153
asked Nov 24 '18 at 3:21
ScottyDScottyD
153
asked Nov 24 '18 at 3:21
ScottyDScottyD
153
asked Nov 24 '18 at 3:21
ScottyDScottyD
153
153
add a comment |
add a comment |
2 Answers
2
active
oldest
votes
Why not
isDuped( ).
isDuped([A, A | C] ) :-
isDuped( C ).
answered Nov 24 '18 at 9:20
joel76joel76
4,87511317
add a comment |
In your code, comparison A == B checks if the terms A and B are identical. An uninstantiated variable and a number are not identical terms.
What your professor seems to want (not clear from the problem formulation you gave, but clear from the test) is unification =: just change A == B to A = B.
answered Nov 24 '18 at 3:33
Sergey DymchenkoSergey Dymchenko
4,44411330
That did the trick. Thanks.
– ScottyD
Nov 24 '18 at 3:39
add a comment |
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2 Answers
2
active
oldest
votes
2 Answers
2
active
oldest
votes
active
oldest
votes
active
oldest
votes
Why not
isDuped( ).
isDuped([A, A | C] ) :-
isDuped( C ).
answered Nov 24 '18 at 9:20
joel76joel76
4,87511317
add a comment |
Why not
isDuped( ).
isDuped([A, A | C] ) :-
isDuped( C ).
answered Nov 24 '18 at 9:20
joel76joel76
4,87511317
add a comment |
Why not
isDuped( ).
isDuped([A, A | C] ) :-
isDuped( C ).
answered Nov 24 '18 at 9:20
joel76joel76
4,87511317
Why not
isDuped( ).
isDuped([A, A | C] ) :-
isDuped( C ).
answered Nov 24 '18 at 9:20
joel76joel76
4,87511317
answered Nov 24 '18 at 9:20
joel76joel76
4,87511317
answered Nov 24 '18 at 9:20
joel76joel76
4,87511317
answered Nov 24 '18 at 9:20
joel76joel76
4,87511317
4,87511317
add a comment |
add a comment |
In your code, comparison A == B checks if the terms A and B are identical. An uninstantiated variable and a number are not identical terms.
What your professor seems to want (not clear from the problem formulation you gave, but clear from the test) is unification =: just change A == B to A = B.
answered Nov 24 '18 at 3:33
Sergey DymchenkoSergey Dymchenko
4,44411330
That did the trick. Thanks.
– ScottyD
Nov 24 '18 at 3:39
add a comment |
In your code, comparison A == B checks if the terms A and B are identical. An uninstantiated variable and a number are not identical terms.
What your professor seems to want (not clear from the problem formulation you gave, but clear from the test) is unification =: just change A == B to A = B.
answered Nov 24 '18 at 3:33
Sergey DymchenkoSergey Dymchenko
4,44411330
That did the trick. Thanks.
– ScottyD
Nov 24 '18 at 3:39
add a comment |
In your code, comparison A == B checks if the terms A and B are identical. An uninstantiated variable and a number are not identical terms.
What your professor seems to want (not clear from the problem formulation you gave, but clear from the test) is unification =: just change A == B to A = B.
answered Nov 24 '18 at 3:33
Sergey DymchenkoSergey Dymchenko
4,44411330
In your code, comparison A == B checks if the terms A and B are identical. An uninstantiated variable and a number are not identical terms.
What your professor seems to want (not clear from the problem formulation you gave, but clear from the test) is unification =: just change A == B to A = B.
answered Nov 24 '18 at 3:33
Sergey DymchenkoSergey Dymchenko
4,44411330
answered Nov 24 '18 at 3:33
Sergey DymchenkoSergey Dymchenko
4,44411330
answered Nov 24 '18 at 3:33
Sergey DymchenkoSergey Dymchenko
4,44411330
answered Nov 24 '18 at 3:33
Sergey DymchenkoSergey Dymchenko
4,44411330
4,44411330
That did the trick. Thanks.
– ScottyD
Nov 24 '18 at 3:39
add a comment |
That did the trick. Thanks.
– ScottyD
Nov 24 '18 at 3:39
That did the trick. Thanks.
– ScottyD
Nov 24 '18 at 3:39
That did the trick. Thanks.
– ScottyD
Nov 24 '18 at 3:39
add a comment |
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