(hons-equal-lite x y) is a non-recursive equality check that optimizes if its arguments are normed.

This documentation topic relates to the experimental extension of ACL2 supporting hash cons, fast alists, and memoization; see hons-and-memoization.

In the logic, hons-equal-lite is just equal; we leave it enabled and would think it odd to ever prove a theorem about it.

Under the hood, hons-equal-lite checks whether its arguments are normed, and if so it effectively becomes a eql check. Otherwise, it immediately calls equal to determine if its arguments are equal.

The idea here is to strike a useful balance between equal and hons-equal. If both arguments happen to be normed, we get to use a very fast equality comparison. Otherwise, we just get out of the way and let equal do its work, without the extra overhead of recursively checking whether the subtrees of x and y are normed.