3ddaf5e32b
Basically, Racklog (and all versions of schelog) implement ! by causing the failure continuation of the entire relation being returned. They did not also cause the unification caused by the relation to be un-done. However, it is not easy to separate un-doing the local changes because the unification just returns a failure continuation too. I had to call that fail continuation but use state to communicate to its target that the next clause should not be visited. I don't know if this is correct. My test suite contains a lot of cut tests that still pass. Erik's test passes too. But I'm not confident that this really works.
20 lines
226 B
Racket
20 lines
226 B
Racket
#lang racket
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(require racklog)
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(define %a
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(%rel (x)
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((x) (%b x))
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((x) (%c x))
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))
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(define %b
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(%rel ()
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((1) !)
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((2))))
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(define %c
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(%rel ()
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((2))))
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(%find-all (x) (%a x))
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