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type_varsl                                                      (Type)
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type_varsl : hol_type list -> hol_type list

SYNOPSIS
Returns the set of type variables in a list of types.

KEYWORDS
variable, type.

DESCRIBE
An invocation {type_varsl [ty1,...,tyn]} returns a list
representing the set-theoretic union of the type variables
occurring in {ty1,...,tyn}.

FAILURE
Never fails.

EXAMPLE

- type_varsl [alpha, beta, bool, ((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_varsl}.

SEEALSO
Type.type_vars, Type.type_var_in, Type.exists_tyvar, Type.polymorphic,
Term.free_vars.

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