Returns a list of the free variables in a list of terms.
DESCRIBE
Found in the hol88 library. When applied to a list of terms, freesl
returns a list of the variables which are free in any of those
terms. There are no repetitions in the list produced even if several
terms contain the same free variable.
FAILURE
Never fails, unless the hol88 library has not been loaded.
EXAMPLE
In the following example there are two free instances each of x and y,
whereas the only instances of z are bound:
- freesl [(--`x+y=2`--), (--`!z. z >= (x-y)`--)];
val it = [(--`x`--),(--`y`--)] : term list
COMMENTS
freesl is not in hol90; use free_varsl instead. WARNING: One can not
depend on the order of the list returned by freesl to be identical to that
returned by free_varsl. They are coded in terms of frees and free_vars,
and thus the discussion in the documentation for frees applies by extension.