CODEWITHSUNDEEP
c++templates
Muhammad
Muhammad

Reputation: 1655

template parameter name as base class

I've the following types:

typedef unsigned int uint32;

typedef void* ptr;

struct memory_options {};

struct memory_provider {};

template <typename options>
struct memory_track {};

template <typename options>
struct no_memory_track : public memory_track<options> {};

template<typename options>
struct defrag_memory_track : public memory_track<options> {};

template<typename options>
struct full_memory_track : public memory_track<options> {};

template <typename options, typename prov, typename track>
struct memory_algorithm : public track < options > {};

int main()
{
}

This types used to define a custom memory manager.

The problem is the class memory_algorithm will inherit from another class, that class will always take a template parameter that represent memory_options class, i call it options. The base class may be a partial specialization from memory_track or a subclass from it, so in memory_algorithm i passed 2 template parameters one represents the class name - i.e. track - and the other represent the memory_options class - i.e. options - now whenever i tried to compile the code with sample test unit using GCC and Visual C++ 2008 i got the error:

for visual c++:

missing ',' before '<'

see reference to class template instantiation 'memory_algorithm' being compiled

for GCC:

error: expected template-name before '<' token

error: expected '{' before '<' token

error: expected unqualified-id before '<' token

What is the problem and how to fix it?

Upvotes: 3

Views: 1291

Answers (1)

Andy Prowl
Andy Prowl

Reputation: 126432

If I understand your question correctly, what you need is probably to make track a template template parameter, rather than a regular type parameter:

template <typename options, typename prov, template<typename> class track> 
//                                         ^^^^^^^^^^^^^^^^^^^^^^^^
struct memory_algorithm : public track < options > {};

Upvotes: 4

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