DCG problem

confusedstudent1 · Dec 3, 2010

I have to write a DCG that generates strings from the alphabet a E {0,1,2} the strings have to have the form nn. This means queries like ?- s([0,2,1,0,2,1],[]). and s([1,1,2,0,1,1,2,0],[]). would return true.

This is the code I have so far. I'm so close. Can someone help me further?

s --> s(X), s(X).
s --> [].

s(0) --> zero, s(X).
s(1) --> one, s(X).
s(2) --> two, s(X).
s(3) --> [].

zero --> [0].
one --> [1].
two --> [2].

Many thanks

kahleen · Dec 3, 2010

Code:

s --> [].
s --> sx, s.

sx --> [0].
sx --> [1].
sx --> [2].

joel76 · Dec 3, 2010

You are very close to the solution !

Just look at these rules
s --> s(X), s(X).
and
s(0) --> zero, s(X).

In the first rule, what is the type of X, an atom or a list ?
In the second rule you use an atom 0, and you introduce X in the body of the rule. You don't have a lot of things to change/add.

joel76 · Dec 3, 2010

No kahleen the production must have the form nn, you accept [0,1,2] for example.

confusedstudent1 · Dec 4, 2010

Great! Thanks joel! I got it!

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DCG problem

confusedstudent1

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kahleen

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joel76

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joel76

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confusedstudent1

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