[GiNaC-list] Can GiNaC set info_flag?

For example, I want to set a symbol r to be rational, or real, but without specifying a value. I know one can use info(info_flags::real) to determine if an object is real, but I want to do the opposite. I found a type 'realsymbol' to do this, but I want many other scopes such as rational, prime, positive integer, pure imaginary, etc. Is there any solution?