Non-failure Analysis (contd.)
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-
Ideally we would like to have a decision procedure to determine
whether a test covers the type of a set of variables.
- Unfortunately this problem is undecidable.
-
In the last period we developed a simple and efficient polynomial time
algorithm which is successful in a significant number of cases.
-
In this period we have identified classes of covering problems which
are decidable and provided special algorithms for them.
- Decidable problems are:
- unification/dis-unification tests, and
tuple-distributive regular types,
which are specified by regular term grammars in which each type
symbol has exactly one defining type rule and each type rule is
deterministic, and
- linear arithmetic tests, and variables of integer or real type.
- (Intuitively) a call will not fail if:
- The type of its input is covered by the test of the corresponding
procedure.
- Each literal in the clauses defining the procedure (recursively)
will not fail.
Thu Jan 18 11:27:49 MET 1996 <herme@fi.upm.es>-<webmaster@clip.dia.fi.upm.es>