Prolog | Unification

Asked Jan 30 '15 at 19:24

Active Jan 30 '15 at 19:24

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I have the follow terms :

3 
p(X)

3
p(x, X)

3
p(x,_)

My question is regarding unification. For example: would "3" unify with "p(X)" [Some p, doesn't matter atm]

Now, my gut feeling is this : First term will unify (X = 3) Second term will unify ( X = 3 ) Third term I'm not sure about, I think that it would too... (As _ = 3)

Anyone that can shed some light on this one for me ? Thanks

asked Jan 30 '15 at 19:24

Aviad

3,424
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p(X) is a purely syntactic term. 3 is a constant/integer. p(X) = 3 fails, regardless of X. – false Jan 30 '15 at 19:28
OK, thanks,but isn't because prolog being backtracking based X is unified before p(X) ? – Aviad Jan 30 '15 at 19:30
2

This has nothing to do with backtracking. To understand unification, it suffices to look at goals like `p(X) = 3` which fails or `p(X) = p(3)` which succeeds with `X = 3`. – false Jan 30 '15 at 19:37
So if I get you right, all three fail? – Aviad Jan 30 '15 at 19:38
yes ................................... – false Jan 30 '15 at 19:41
Alright thank you, please write this as answer so I can vote – Aviad Jan 30 '15 at 19:42

Prolog | Unification

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