c++ - g++ "is not a type" error

Question

Writing a templated function, I declared:

template <typename T>
T invertible(T const& container, T::size_type startIndex, T::size_type endIndex);

Compiling with g++ 4.0.1 I got the error:

error: 'T::size_type' is not a type

Answer 1

You need to add typename.

I.e.

template <typename T>
T invertible(T const& container, typename T::size_type startIndex, typename T::size_type endIndex);

Without having any information on your type T, the compiler needs to know that T::size_type designates a type.

From the standard, section 14.6.2:

A name used in a template declaration or definition and that is dependent on a template-parameter is assumed not to name a type unless the applicable name lookup finds a type name or the name is qualified by the keyword typename.