to_f

static VALUE
nucomp_to_f(VALUE self)
{
    get_dat1(self);

    if (k_inexact_p(dat->imag) || f_nonzero_p(dat->imag)) {
        VALUE s = f_to_s(self);
        rb_raise(rb_eRangeError, "can't convert %s into Float",
                 StringValuePtr(s));
    }
    return f_to_f(dat->real);
}