CODEWITHSUNDEEP
c++templatestypedef
Aly
Aly

Reputation: 16255

C++: Using templated typedef in two classes

Hi I have the following classes:

template<class T>
class RandomTree<T> {
private:
    RandomTreeNode root;
    typedef double (*funcion_ptr) (T, T);

public:
    RandomTree(std::vector<function_ptr> functions){...}
};

template<class T>
class RandomTreeNode<T> {
private:
    typedef double (*funcion_ptr) (T, T);
    function_ptr function;
public:
    RandomTreeNode(function_ptr function){...}
};

The tree is given a vector of function pointers and each node is created and has one particular function. Is there a way for me to not have to define the typedef double (*function_ptr) (T,T) in both classes?

Upvotes: 1

Views: 170

Answers (3)

Some programmer dude
Some programmer dude

Reputation: 409166

As you are declaring a free-standing function pointer type, as opposed to a member-function pointer, you could of course put the typedef in a separate templated class in global scope or in a namespace, so it can be accessed by both classes.

Like this:

template<class T>
struct RandomTreeFunction
{
    typedef double (*function_ptr)(T, T);
};

template<class T>
class RandomTree<T> {
private:
    typedef typename RandomTreeFunction<T>::function_ptr function_ptr;
    ...
};

I also recommend you to look into using std::function instead.

Upvotes: 3

TemplateRex
TemplateRex

Reputation: 70516

If you have acccess to a compiler (e.g. gcc >= 4.7, clang >= 3.0) that supports template aliases, you can do something like

#include <vector>

template<class T>
using function_ptr = double (*)(T,T);  

template<class T>
class RandomTreeNode {
private:
    function_ptr<T> function;
public:
    RandomTreeNode(function_ptr<T> function){/*...*/}
};

template<class T>
class RandomTree {
private:
    RandomTreeNode<T> root;

public:
    RandomTree(std::vector<function_ptr<T>> functions){/*...*/}
};

Otherwise, the solution by Joachim Pileborg is adequate.

Upvotes: 0

detunized
detunized

Reputation: 15289

If you make it public in RandomTreeNode<T> you can say then:

template<class T>
class RandomTree<T> {
    typedef RandomTreeNode<T>::funcion_ptr function_ptr;
};

or use RandomTreeNode<T>::funcion_ptr directly, which would be quite tedious.

Upvotes: 0

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