Question

i have a question regaring c++ and arrays.

let say i have a class which is called CustomArray, and is nothing more than an generic array wich has attributes for size and capacity, to make the array dynamic. defined as:

template<typename T>
class CustomArray
{
public:
    int capacity, size;
    T* items;
    //constructor

    //destructor

    //function1

    //function2

    //etc...
};

now i’m kinda stuck, i want to implement a function like:”

void performOnAllItems(/*function?*/)
{
    for(int i = 0; i < size; i++)
    {
        //perform function on element
    }
}

that takes another function as a parameter (if that is possible?) and performs it on all elements. is that possible? and if so… how?

thanks in advance.

Answer 1

Add members begin and end like so:

T *begin() { return items; }

T *end() { return items + size; }

Create a functor that derives from std::unary_function.

E.g.

template <typename T>
class MyFunc : std::unary_function<T, void> {
public:
    void operator()(T& t) {
    // ...
    }
};

Then call std::foreach(foo.begin(), foo.end(), MyFunc);

Update

In C++11, you can use a lambda for the foreach:

std::foreach(foo.begin(), foo.end(),
              [/* (1) */](T& t) { /* ... */ }
            ); 

If (1) isn’t empty, then the lambda is a closure; this is known as a capturing lambda, and Visual C++ 10 Lambda Expressions provides a nice example of this.