Enum within a class

Code:

---

#include<string>
#include<sstream>
#include<iostream>
using namespace std;
class token
{
    std::string ori_val;
    public:
    token(std::string);
    enum optype{oprnd,add,sub,mul,div,sin,cos,tan,log};
    optype opt;
    double num;

    char sng_oprt;
    //std::string str_oprt;

};
token::token(std::string input)
{
    ori_val=input;
    istringstream in;
    in.str(input);
    char c;
    std::string str;
    double num_in;
    if(in>>c)
    {
        sng_oprt=c;
        switch (c)
        {
            case '+':opt=token::add;break;
            case '-':opt=token::sub;break;
            case '*':opt=token::mul;break;
            case '/':opt=token::div;break;
        }
        in.clear();
    }
    else if(in>>num_in)
    {
        num=num_in;
        opt = token::oprnd;
        in.clear();
    }
    else if(in>>str)
    {

        switch (str[0])
        {
            case 's':opt=token::sin;break;
            case 'c':opt=token::cos;break;
            case 't':opt=token::tan;break;
            case 'l':opt=token::log;break;
        }

    }



}

int main()
{
    token t("sin");
    cout<<t.opt;
    return 0;
}

---

Shouldn't the enum value for sin be 5 ? Instead it is always returning a garbage value. Did I miss anything important about enumeration types?

You know, "if(in>>c)" will always be true if 'input' is more that 1 characters long.

o...I thought that giving a whole string to a character input would return false..
Anyway..after it being true would the character c contain the first letter from the string or a random value?