Understand the STL

Understanding STL

I want to understand the Standard Template Library (STL) in excruciating detail and the best way is to implement it. I’m starting off with std::vector as it is relatively simple algorithmitically but a fundamental container.

This is not intended for production use. It is targetting C++-17 with a little bit of C++-20. There’s no attempt to be portable or backward compatible beyond following good practices. There’s no obfuscating names with __ to avoid conflicts with other code.

Ideally, no std code is used. However, <limits> and <stdexcept> are used from std because it seems like a lot of work for not much gain.

The namespace is pw and include files are pw/<name>. Most of the actual implementations are in pw/impl/<file.h>. In fact, most of the STL include files consist primarily of including various implementation files.

The namespace pw::internal is for private details and are in pw/internal/<file.h>. These should not be used by other code.

Unit tests are in tests/unit/<file.t.cpp> and use the catch2 framework.

How to proceed

An iterative process of writing code to implement vector and when that requires other code from STL digress until that other code is done.

Depending on the complexity or need these digressions may not fully implement the standard.

The declaration

Here is the first step pw_vector.h:

#ifndef PW_VECTOR_H
#define PW_VECTOR_H

namespace pw {

template<class Type, class Allocator>
class vector
{
public:
};
}

#endif /*  PW_VECTOR_H */

and the first digression: the Allocator needs a default allocator.