The NORMEQ_ss simpset fragment embodies a conversion that flips
terms of the form l = r when l contains no free variables, and r
contains at least one variable. To flip an equality is to rewrite it
so that l = r becomes r = l.
As a static value, this cannot fail.
In this example, the simplifier flips the 3 = x term, making it
useful as a rewrite when attacking the consequent of the implication.
SIMP_CONV (bool_ss ++ boolSimps.NORMEQ_ss)  ``(3 = x) ==> x + 1 < y``;
> val it =
|- (3 = x) ==> x + 1 < y <=> (x = 3) ==> 3 + 1 < y : thm