\DOC mk_thy_const

\TYPE {mk_thy_const : {Thy:string, Name:string, Ty:hol_type} -> term}

\SYNOPSIS
Constructs a constant.

\DESCRIBE
If {n} is a string that has been previously declared to be a constant
with type {ty} in theory {thy}, and {ty1} is an instance of {ty},
then {mk_thy_const{Name=n, Thy=thy, Ty=ty1}} returns the specified
instance of the constant.

(A type {ty1} is an 'instance' of a type {ty2} when {match_type ty2 ty1}
does not fail.)

\FAILURE
Fails if {n} is not the name of a constant in theory {thy}, if {thy} is
not in the ancestry of the current theory, or if {ty1} is not an
instance of {ty}.

\EXAMPLE
{
   - mk_thy_const {Name="T", Thy="bool", Ty=bool};
   > val it = `T` : term

   - try mk_thy_const {Name = "bar", Thy="foo", Ty=bool};
   Exception raised at Term.mk_thy_const:
   "foo$bar" not found
}


\SEEALSO
Term.dest_thy_const, Term.mk_const, Term.dest_const, Term.is_const, Term.mk_var, Term.mk_comb, Term.mk_abs, Type.match_type.
\ENDDOC