next up previous contents
Next: 5.5 Iterating through a Up: 5 Querying Existing Relations Previous: 5.3 Simplification and satisfiability

5.4 Querying variables

The function Relation::global_decls() returns a pointer to the collection of Variable_ID s that contains all the uses of global variables in the relation. This collection may include some global variables that have been eliminated during simplification.

The function Relation::query_difference(Variable_ID v1, Variable_ID v2, int &lowerBound, int &upperBound, bool &guaranteed) can be used to determine bounds on the possible value of v1 - v2 . Note that these bounds are not necessarily tight. After this call, guaranteed will be true if these bounds are guaranteed to be tight. If the difference is not bounded below, lowerBound will be negInfinity . If the difference is not bounded above, upperBound will be posInfinity . These constants are defined in `` oc.h '', which is included by `` omega.h ''.