if(vartype==1) stream>>vartype1;
else if(vartype==2) stream>>vartype2;
...

if(vartype==1) sscanf(string, "%f", &vartype1);
else if(vartype==2) sscanf(string, "%d", &vartype2);

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

class multitype
{
public:
        multitype(const char *i):e(strdup(i)),type(T_CSTRING)   { }
        multitype(float i):c(i),type(T_FLOAT)   { }
        multitype(char i):b(i),type(T_CHAR)             { }
        multitype(int i):a(i),type(T_INT)               { }

        inline operator int() const     { return(a); }
        inline operator float() const   { return(c); }
        inline operator char() const    { return(b); }
        inline operator const char *() const    { return(e); }

        ~multitype()
        {       if(type==T_CSTRING) free(e);            }

protected:
        enum { T_INT, T_CHAR, T_FLOAT, T_DOUBLE, T_CSTRING } type;

        // All members of a union occupy the SAME memory.
        // You can't use more than one at once.
        union
        {
                int a;
                char b;
                float c;
                char *e;
                // You cannot put classes in a union though, since it won't know
                // which constructor to use!
        };
};

int main(int argc, char *argv[])
{
        multitype str("asdf"), f(3.14159f), i(32);

        printf("string %s float %f int %d\n", (const char *)str,
                (float)f, (int)i);
        return(0);
}