Question

Why can’t I do this:

struct sName {
  vector<int> x;
};

It takes only three pointers to store a vector, so I should be able to do this?

Answer 1

You mentioned this failed in a switch statement. You’ll need to wrap it up in an extra pair of braces:

int type = UNKNOWN;
switch(type)
{
  case UNKNOWN:
    cout << "try again" << endl;
    break;
  case KNOWN:
  { // Note the extra braces here...
    struct sName
    { 
      vector<int> x;
    } myVector; 
  } // and here
}

Alternatively, you could have already declared the structure, and are just trying to declare and initialize a local variable. This isn’t a problem unique to struct, it’ll happen anytime you try to initialize a variable inside a case:

struct sName
{ 
  vector<int> x;
};

int type = UNKNOWN;
switch(type)
{
  case UNKNOWN:
    cout << "try again" << endl;
    break;
  case KNOWN:
  { // Note the extra braces here...
    sName myVector;
  } // and here
  case OTHER:
    int invalid = 0; // this will also fail without the extra pair of braces
    break;
}