I'm working my way through Leino's "Program Proofs" and I was following as far as the semantics of variable assignment, but I'm not quite sure why this is a valid Hoare triple:
{forall x::Q} var x; {exists x :: P}
where P is the weakest precondition and Q is the strongest postcondition. I'm not following why allocating x guarantees that there exists an x that satisfies P.
