Thread: Compiler Error: Unsigned vs Signed Integer Expression

RentalSystem.cpp:357: warning: comparison between signed and unsigned integer expressions

I have a number of these errors in basically the same situation. Line 357 is :

Code:

for ( i = 0; i < m_vehicleVector.size(); i++ )

m_vehicleVector is declared as :

Code:

vector<T> m_vehicleVector;

It's declares as a private data member in a class template RentalSystem.cpp.

Code:

RentalSystem <NewCar> Rental

With NewCar being another class. Now I'm new to templates, so I'd imagine I'm doing something wrong with my templates, but I can't see it. Any ideas?

Thanks in advance,
Chris

Use vector<T>::size_type as the type for i.

hk_mp5kpdw, my fault, they were warnings, not errors. I understand that the warning is telling me that it's trying to compare unsigned and signed ints. I tried declaring i as simply:

Code:

unsigned int i;

but it didn't resolve the warnings. Also, daved, I'm not sure I understand the syntax of what you're trying to tell me to do. Sorry, could you clarify?

Use

Code:

vector<T>::size_type i;

instead of

Code:

int i;

because the type returned by vector.size() is vector<T>::size_type, which is just a typedef for an unsigned integral type. This way you won't have any mismatches, because they will be of the same type.

The compiler threw a warning at me for trying that.

Code:

RentalSystem.cpp: In member function `void
   RentalSystem<T>::ReadCommands(std::vector<type, std::allocator<type> >&,
   std::vector<assoc, std::allocator<assoc> >&, std::ifstream&)':
RentalSystem.cpp:298: warning: `typename std::vector<T, std::allocator<_CharT>
   >::size_type' is implicitly a typename
RentalSystem.cpp:298: warning: implicit typename is deprecated, please see the
   documentation for details