type_vars : hol_type -> hol_type list
STRUCTURE
SYNOPSIS
Returns the set of type variables in a type.
DESCRIPTION
An invocation type_vars ty returns a list representing the set of type variables occurring in ty.
FAILURE
Never fails.
EXAMPLE
- type_vars ((alpha --> beta) --> bool --> beta);
> val it = [`:'a`, `:'b`] : hol_type list

COMMENTS
Code should not depend on how elements are arranged in the result of type_vars.
SEEALSO
HOL  Kananaskis-14