FVL : term list -> term set -> term set
STRUCTURE
Term
SYNOPSIS
Efficient computation of the set of free variables in a list of terms.
DESCRIPTION
An invocation FVL [t1,...,tn] V adds the set of free variables found in t1,...,tn to the accumulator V.
FAILURE
Never fails.
EXAMPLE
- FVL [Term `v1 /\ v2 ==> v2 \/ v3`] empty_varset;
> val it = <set> : term set

- HOLset.listItems it;
> val it = [`v1`, `v2`, `v3`] : term list

COMMENTS
Preferable to free_varsl when the number of free variables becomes large.
SEEALSO
HOLset, empty_varset, free_varsl, free_vars
HOL  Kananaskis-14