This pseudocode shows the fail-soft variation of alpha-beta pruning.

The pseudo-code for the fail-soft variation of alpha-beta pruning is as follows:

But theyre fail-soft.

Over time, other improvements have been suggested, and indeed the Falphabeta (fail-soft alpha-beta) idea of Fishburn is nearly universal and is already incorporated above in a slightly modified form.

And it's a fail soft solution, that is, if either one doesn't, you just don't get authentication.