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@@ -1,9 +1,13 @@
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---
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-icon: dot
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-label: 'Bind native function'
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-order: 60
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+icon: star
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+title: Write bindings
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+order: 18
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---
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+!!!
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+This document is working in progress.
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+!!!
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+
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pkpy allows to wrap a function pointer as a python function or method that can be called in python code.
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This function pointer has the following signature:
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@@ -100,4 +104,105 @@ vm->bind__add__(type, __add__);
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This specialized binding function has optimizations and result in better performance when calling from python code.
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-For example, `vm->bind__add__` is preferred over `vm->bind_method<1>(type, "__add__", ...)`.
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+For example, `vm->bind__add__` is preferred over `vm->bind_method<1>(type, "__add__", ...)`.
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+
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+Add `PY_CLASS` macro into your `struct` and implement a static function `_register`.
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+Inside the `_register` function, you can bind methods and properties to the class.
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+
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+```cpp
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+PY_CLASS(T, mod, name)
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+
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+// T is the struct type in cpp
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+// mod is the module name in python
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+// name is the class name in python
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+```
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+
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+## Example
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+
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+In this example, we will create a `linalg` module
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+and implement a `vec2` type with some methods.
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+And make them available in python just like this.
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+
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+```python
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+from linalg import vec2
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+
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+# construct a vec2
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+a = vec2(1.0, 2.0)
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+b = vec2(0.0, -1.0)
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+
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+# add two vec2
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+print(a + b) # vec2(1.0, 1.0)
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+
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+# set x component
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+a.x = 8.0
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+print(a) # vec2(8.0, 2.0)
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+
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+# use dot method
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+print(a.dot(b)) # -2.0
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+```
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+
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+### Implement `Vec2` struct in cpp
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+
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+```cpp
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+struct Vec2{
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+ float x, y;
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+ Vec2() : x(0.0f), y(0.0f) {}
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+ Vec2(float x, float y) : x(x), y(y) {}
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+ Vec2(const Vec2& v) : x(v.x), y(v.y) {}
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+ Vec2 operator+(const Vec2& v) const { return Vec2(x + v.x, y + v.y); }
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+ float dot(const Vec2& v) const { return x * v.x + y * v.y; }
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+};
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+```
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+
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+### Create `PyVec2` wrapper
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+
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+```cpp
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+struct PyVec2: Vec2 {
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+ PY_CLASS(PyVec2, linalg, vec2)
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+
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+ PyVec2() : Vec2() {}
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+ PyVec2(const Vec2& v) : Vec2(v) {}
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+ PyVec2(const PyVec2& v) : Vec2(v) {}
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+
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+ static void _register(VM* vm, PyObject* mod, PyObject* type){
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+ vm->bind_constructor<3>(type, [](VM* vm, ArgsView args){
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+ float x = CAST_F(args[1]);
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+ float y = CAST_F(args[2]);
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+ return VAR(Vec2(x, y));
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+ });
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+
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+ vm->bind__repr__(PK_OBJ_GET(Type, type), [](VM* vm, PyObject* obj){
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+ PyVec2& self = _CAST(PyVec2&, obj);
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+ std::stringstream ss;
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+ ss << "vec2(" << self.x << ", " << self.y << ")";
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+ return VAR(ss.str());
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+ });
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+
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+ vm->bind__add__(PK_OBJ_GET(Type, type), [](VM* vm, PyObject* obj, PyObject* other){
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+ PyVec2& self = _CAST(PyVec2&, obj);
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+ PyVec2& other_ = CAST(PyVec2&, other);
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+ return VAR_T(PyVec2, self + other_);
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+ });
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+
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+ vm->bind(type, "dot(self, other: vec2) -> float", [](VM* vm, ArgsView args){
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+ PyVec2& self = _CAST(PyVec2&, args[0]);
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+ PyVec2& other = CAST(PyVec2&, args[1]);
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+ return VAR(self.dot(other));
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+ });
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+ }
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+};
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+```
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+
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+### Create `linalg` module
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+
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+```cpp
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+void add_module_linalg(VM* vm){
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+ PyObject* linalg = vm->new_module("linalg");
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+ // register PyVec2
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+ PyVec2::register_class(vm, linalg);
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+}
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+```
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+
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+### Further reading
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+
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+See [linalg.h](https://github.com/blueloveTH/pocketpy/blob/main/src/linalg.h) for the complete implementation.
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