- iset-adjoin! iset element1 element2 …procedure
The `iset-adjoin!` procedure is the same as `iset-adjoin`, except that it is permitted to mutate and return the iset argument rather than allocating a new iset.
The `iset-adjoin!` procedure is the same as `iset-adjoin`, except that it is permitted to mutate and return the iset argument rather than allocating a new iset.