# C++ Pimpl

**[Pimpl](https://en.cppreference.com/w/cpp/language/pimpl)** (Pointer to Implementation) is a design pattern that hides implementation details behind a pointer, reducing compilation dependencies and enabling binary compatibility across library versions. The public header declares only the interface; the actual implementation lives in a separate private class.

Use Pimpl to decouple the public API from implementation details and reduce header file bloat.

## Example

This example shows how Pimpl separates interface from implementation to minimize compilation dependencies.

```cpp
// compile: g++ -o pimpl pimpl.cpp
// run: ./pimpl
// description: Pimpl pattern decouples interface from implementation

#include <iostream>
#include <memory>

class Widget {
public:
    Widget();
    ~Widget();
    void draw();
private:
    class Impl;
    std::unique_ptr<Impl> pimpl;
};

class Widget::Impl {
public:
    void draw() { std::cout << "Drawing widget\n"; }
};

Widget::Widget() : pimpl(std::make_unique<Impl>()) {}
Widget::~Widget() = default;

void Widget::draw() { pimpl->draw(); }

int main() {
    Widget w;
    w.draw();
    return 0;
}
```