leon.proof
Relational reasoning.
{ ((y :: ys) :+ x).last _ == _ | trivial | (y :: (ys :+ x)).last ==| trivial | (ys :+ x).last ==| snocLast(ys, x) | x }.qed
Short-hand for equational reasoning.
Relational reasoning.
{ ((y :: ys) :+ x).last _ == _ | trivial | (y :: (ys :+ x)).last ==| trivial | (ys :+ x).last ==| snocLast(ys, x) | x }.qed