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Is it possible to declare a function in header file with unknown type that is specified only in file '.c'?


By : Govardana Reddy
Date : September 14 2020, 12:00 AM
will be helpful for those in need I can give specific details of implementation if needed but the general question is the following: , Your comment:
code :
//forward-declare the structs (assuming tag = typedef_name)
struct secp256k1_context;
struct secp256k1_ge;
struct secp256k1_pubkey;
//use struct tag instead of typedef_name
int secp256k1_pubkey_load(const struct secp256k1_context* ctx, 
                          struct secp256k1_ge* ge, 
                          const struct secp256k1_pubkey* pubkey);


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how to declare type conversion in header file and implement in cpp file?


By : Rakesh Raut
Date : March 29 2020, 07:55 AM
this will help I also wanted to separate the class declaration from the implementation. The critical missing ingredient was the const:
code :
// Foobar.hpp
class Foobar
{
    public:
        Foobar() : _v(42) {}

        operator int() const;

    private:

        int _v;
};
#include "Foobar.hpp"

Foobar::operator int() const
{
    return _v;
}

How to declare a class function in header file in cpp file?


By : Tom Dell
Date : March 29 2020, 07:55 AM
To fix the issue you can do For example in the following code: , You need to put the return type before the class name:
code :
void mixedFraction::add (mixedFraction f) {
     //...
}

Should I include <stdio.h> in my header file, just so I can declare a function that takes a FILE*?


By : John K
Date : March 29 2020, 07:55 AM
fixed the issue. Will look into that further Short answer: you are trying to solve a non-existing problem.
If you use FILE, you include stdio.h or cstdio in C++. It's that simple.

How to declare array of same class type in header file?


By : Siva
Date : March 29 2020, 07:55 AM
it should still fix some issue A class cannot contain instances of itself. Doing so would require the class to be infinitely large, since each sub-object would contain a sub-sub-object, which would contain a sub-sub-sub-object, etc.
What a class can contain, is pointers to objects of its own type. Since a pointer can be null, it's possible to stop the infinite loop and only have a finite number of objects.
code :
class QuadTree
{
public:
    QuadTree() : nodes_{nullptr}
    {
    }

    ~QuadTree() { delete[] nodes_; }

    // I've deleted these to make a QuadTree non-copyable.
    // You'll need to implement them to do a deep copy if you want that
    QuadTree(const QuadTree& other) = delete;
    QuadTree& operator=(const QuadTree& other) = delete;

    void Clear();

    void split() {
        nodes_ = new QuadTree[4] {
            { /* TODO QuadTree args */ },
            { /* TODO QuadTree args */ },
            { /* TODO QuadTree args */ },
            { /* TODO QuadTree args */ }
        };
    }

private:
    QuadTree* nodes_;
};
class QuadTree
{
public:
    // No longer have to explicitly initialize nodes_ to nullptr
    // since a default-constructed unique_ptr is null
    QuadTree();

    // No longer need to delete[] here; unique_ptr handles that for us
    ~QuadTree();

    // Copy constructor and assignment are now implicitly deleted since
    // unique_ptr is non-copyable.
    // You'll need to implement them to do a deep copy if you want that

    void Clear();

    void split() {
        nodes_.reset(new QuadTree[4] {
            { /* TODO QuadTree args */ },
            { /* TODO QuadTree args */ },
            { /* TODO QuadTree args */ },
            { /* TODO QuadTree args */ }
        });
    }

private:
    std::unique_ptr<QuadTree[]> nodes_;
};
class QuadTree
{
public:
    QuadTree();
    ~QuadTree();

    // QuadTree is now implicitly copyable, since std::vector does a deep-copy by default

    void Clear();

    void split() {
        nodes_ = {
            { /* TODO QuadTree args */ },
            { /* TODO QuadTree args */ },
            { /* TODO QuadTree args */ },
            { /* TODO QuadTree args */ }
        };
    }

private:
    std::vector<QuadTree> nodes_;
};

Can I declare a function in a C source file without declaring it in the header file?


By : Himanshu Kumar
Date : March 29 2020, 07:55 AM
wish helps you Yes, you certainly can include the declaration in your source file. Make sure that the declaration comes before the usage of the function.
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