In their maximal generality, simplification operations in HOL Light (as invoked
by SIMP_TAC) are controlled by a `simpset', which may contain conditional and
unconditional rewrite rules, conversions and provers for conditions, as well as
a determination of how to use the prover on the conditions and how to process
theorems into rewrites. A call ss_of_provers prs ss adds the provers in prs
to the simpset ss to yield a new simpset. See mk_prover for more
explanation of how to create something of type prover.