hol88Lib.frees : term -> term list
- frees (--`(x=1) /\ (y=2) /\ (!z. z >= 0)`--); > val it = [(--`x`--),(--`y`--)] : term list
- val tm = (--`x (y:num):bool`--); > val tm = (--`x y`--) : term - free_vars tm > val it = [(--`y`--),(--`x`--)] : term list - frees tm; > val it = [(--`x`--),(--`y`--)] : term listIt ought to be the case that the result of a call to frees (or free_vars) is treated as a set, that is, the order of the free variables should be immaterial. This is sometimes not possible; for example the result of gen_all (and hence the results of GEN_ALL and new_axiom) necessarily depends on the order of the variables returned from frees. The problem comes when users write code that depends on the order of quantification. For example, contrary to some expectations, it is not the case that (tm being a closed term already)
GEN_ALL (SPEC_ALL tm) = tmwhere ``='' is interpreted as identity or alpha-convertibility.