... Leavens1
Leavens's work was supported in part by NSF grants CCR-9593168 and CCR-9803843.
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... operator2
The specifications in Object Orientation in Z [45] are a bit vague on exactly what capabilities are needed by the scalar type. As there is no easy way to implement an exact length function (because some lengths are irrational) the specification in PreVector allows the length operator to return an approximate result.
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... clause3
Following Leino's work [34], if an object o mentioned in a modifies clause has been declared to depend on some other object o', then o' may also be modified. The same qualification is also applied to the trashes clause. But this qualification is not needed to understand the examples in this paper.
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... variables4
Indeed, Larch/C++ is the only Larch-style BISL for which abstract models can be given by using specification variables.
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Gary T. Leavens
1999-01-26