# Structure Cond_rewr

(* ----------------------------------------------------------------------
COND_REWR_CONV : thm -> bool -> (term -> thm) -> conv
Build a conversion based on a conditional rewrite theorem. The
theorem must be of the form
A |- P1 ==> ... Pm ==> (Q[x1,...,xn] = R[x1,...,xn])
The conversion matches the input term against Q, using limited
higher order matching. This instantiates x1 ... xn, which the
conversion then solves with the solver provided. If any of the
conditions are not solved COND_REWR_CONV fails.
The theorem can be a permutative rewrite, such as
|- (x = y) = (y = x)
|- (x + y) = (y + x)
In these cases the rewrite will be applied if
* the ordering of the variables in the term is not in strictly
ascending order, according to a term_lt function which places
a total ordering on terms (Nb. The term ordering needs to be
"AC" compatible - see Termord); or
* if the boolean argument is true, which happens if the theorem
being used is a bounded rewrite, and so cannot cause a loop
when it is used.
FAILURE CONDITIONS
Fails if any of the assumptions cannot be solved by the solver,
or if the term does not match the rewrite in the first place.
---------------------------------------------------------------------- *)
signature Cond_rewr =
sig
include Abbrev
type controlled_thm = BoundedRewrites.controlled_thm
val ac_term_ord : term * term -> order
val mk_cond_rewrs : controlled_thm -> controlled_thm list
val IMP_EQ_CANON : controlled_thm -> controlled_thm list
val COND_REWR_CONV : thm -> bool ->
(term list -> term -> thm) -> term list -> conv
val QUANTIFY_CONDITIONS : controlled_thm -> controlled_thm list
val stack_limit : int ref
val used_rewrites : thm list ref
val track_rewrites : bool ref
end

*HOL 4, Kananaskis-11*