Lean is a theorem prover and programming language. Attempts have also been made to validate Anselm's proof using an automated theorem prover. Typically, some form of automated theorem prover is used to discharge verification conditions. Coq is an interactive theorem prover first released in 1989. HOL Light is a member of the HOL theorem prover family. Their goal was to make a fully automatic, logic-based theorem prover. Gordon led the development of the HOL theorem prover. IBM used ACL2, a theorem prover, in AMD x86 processor development process. It is an LCF-style theorem prover (written in Standard ML). His research is based around the interactive theorem prover Isabelle, which he introduced in 1986. There is a built-in geometry theorem prover (based on the area method). Recently he has built a new theorem prover, MetiTarski, for real-valued special functions. Water Draws, LLC is a pipe prover calibrating company. Thus, a cheating prover has a 0.5 probability of successfully cheating in one round. The product family consists of Polyspace Code Prover and Polyspace Bug Finder.