Question

I’m getting an error occurring in the vector class, as in, the class which you access when you #include < vector >

I it get only once, and I don’t have a clue why it would be occurring:

error C2036: 'Agent *const ' : unknown size

This is also occurring in vector, and the code that has the error is here:

size_type size() const
{   // return length of sequence
    return (this->_Mylast - this->_Myfirst); // error on this line
}

Answer 1

This mean that the type Agent is not fully known at this point. You probably just have forward-declared it, but don’t have a definition visible at this point.

The following piece of code exhibit this error:

#include <vector>
class Agent;
static int getSize(std::vector< Agent > const& v) {
    return v.size();
}

What you need is to include the file that define the Agent class before you use a std::vector< Agent >. The file is probably named Agent.h.

The reason for the error is because in the line of code you pointed, the compiler try to compute the difference between two Agent const*. This is roughly equal to the difference of the pointer casted to char const* divided by sizeof(Agent). However, this size is not know if the type is not fully defined.