using same datatype in boost variant

Question

Can we explicitly typecast the value which is to be stored in boost varaint??

Example:

typedef int abc;

typedef int asd;

typedef boost::variant<abc, char, asd, float> link_try1;

int main()
{

  link_try1 qw;
  qw = static_cast<asd>(1234);
  printf("value of which is:%d", qw.which());
  return 0;
}

Here I want the which() function to retrun 3 but it always retruns 0. Is there a way of directly changing the value in which_ (private variable in class variant) or explicitly specifying the datatype to be used??

Regards Ankith

score 7 · Accepted Answer · answered Apr 28 '11 at 06:28

It is possible, but it won't work as expected.

The key idea, on a variant, is that the type acts as a key. When you actually request a given type (using boost::get or visitation), the first type in the variant that matches the key is elected, thus here asd would be haughtily ignored.

If you need to store several integers for different purposes, you can use BOOST_STRONG_TYPEDEF to create different integer-like classes and use those in the variant.

using same datatype in boost variant

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