File: tyvars.doc

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\DOC tyvars

\TYPE {tyvars : (term -> type list)}

\SYNOPSIS
Returns a list of the type variables free in a term.

\DESCRIBE
When applied to a term, {tyvars} returns a list (possibly empty) of the type
variables which are free in the term.

\FAILURE
Never fails.

\EXAMPLE
{
#PAIR;;
|- !x. FST x,SND x = x

#tyvars (concl PAIR);;
[":*"; ":**"] : type list

#tyvars "x + 1 = SUC x";;
[] : type list
}
\COMMENTS
In the current HOL logic, there is no binding operation for types, so `is free
in' is synonymous with `appears in'.

\SEEALSO
tyvarsl.

\ENDDOC