/**
* Checks to see if the same invariant exists over supersequences of these variables:
*
* <p>(A[] op B[]) ^ (i == j) ==> A[i..] op B[j..] (A[] op B[]) ^ (i == j) ==> A[..i] op B[..j]
*/
private DiscardInfo superseq_implies(VarInfo[] vis) {
// Make sure the variables are SequenceScalarSubsequence with the same start/end
VarInfo v1 = vis[0];
VarInfo v2 = vis[1];
if (!v1.isDerived() || !(v1.derived instanceof SequenceScalarSubsequence)) return (null);
if (!v2.isDerived() || !(v2.derived instanceof SequenceScalarSubsequence)) return (null);
SequenceScalarSubsequence der1 = (SequenceScalarSubsequence) v1.derived;
SequenceScalarSubsequence der2 = (SequenceScalarSubsequence) v2.derived;
if ((der1.from_start != der2.from_start) || (der1.index_shift != der2.index_shift))
return (null);
// Make sure the subscripts are equal
DiscardInfo di = new DiscardInfo(this, DiscardCode.obvious, "");
if (!ppt.parent.check_implied_canonical(di, der1.sclvar(), der2.sclvar(), IntEqual.get_proto()))
return (null);
// See if the super-sequences have the same invariant
if (!ppt.parent.check_implied_canonical(
di, der1.seqvar(), der2.seqvar(), PairwiseIntLessThan.get_proto())) return (null);
// Add in the vis variables to di reason (if they are different)
di.add_implied_vis(vis);
return (di);
}
