feat: BitVec.toInt_neg_eq_ite #6153
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This PR adds a theorem that describes `(-x).toInt` as a case-split: - If `x = intMin w`, then `(-x)` overflows and is equal to `intMin w = x = -x`. and thus `(-x).toInt = x.toInt`. - otherwise, `(-x).toInt = - (x.toInt)`. This is a building block to prove `BitVec.toInt_abs`, from leanprover#5787
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This is already in #6154, right? |
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This PR adds a theorem that describes
(-x).toIntas a case-split:x = intMin w, then(-x)overflows and is equal tointMin w = x = -x. and thus(-x).toInt = x.toInt.(-x).toInt = - (x.toInt).This better matches the semantics one might expect of such an operation, since, in particular, it explicitly describes what happens when
x = intMin, and it combines two existing lemmas on the two sides of the case split:neg_intMin,toInt_neg_of_ne_intMin