#!/usr/bin/env python
# coding: utf-8

# # pybind11: Use C++ libraries
# 
# 
# [pybind11](https://pybind11.readthedocs.io) lets you write Python extensions using pure C++; no special tool or processing step needed. It's just a header-only library that works just about everywhere. Used by SciPy, PyTorch, and many more libraries.

# ## Example
# 
# A Python extension in pybind11 looks like this:
# 
# ---
# 
# ```cpp
# #include <pybind11/pybind11.h>
# 
# namespace py = pybind11;
# 
# int square(int x) {
#     return x * x;
# }
# 
# PYBIND11_MODULE(somecode, m) {
#     m.def("square", &square);
# }
# ```
# 
# ---

# You can use `cppimport` to import it for a quick test, or a build system like scikit-build-core to build. I'm not including a compiler in this environment, so I'm not going to build here - see one of my other classes. This is a minimal `CMakeLists.txt`:
# 
# ---
# 
# ```cmake
# cmake_minimium_required(VERSION 3.15...3.26)
# project(python_example LANGUAGES CXX)
# 
# set(PYBIND11_FINDPYTHON ON)
# find_package(pybind11 CONFIG REQUIRED)
# 
# pybind11_add_module(python_example MODULE src/main.cpp)
# 
# install(TARGETS python_example DESTINATION .)
# ```
# 
# ---

# And, your pyproject.toml:
# 
# 
# ---
# 
# ```toml
# [build-system]
# requires = ["scikit-build-core", "pybind11"]
# build-backend = "scikit_build_core.build"
# 
# [project]
# name = "example"
# version = "0.0.1"
# requires-python = ">=3.8"
# ```
# ---

# If you want to build and distribute, use [cibuildwheel](https://cibuildwheel.readthedocs.io), which is used by Scikit-Learn, Matplotlib, MyPy, and many more; it can be setup for Linux, macOS, and Windows and all common CPython and PyPy versions in just 13 lines:
# 
# ---
# 
# ```yaml
# on: [push, pull_request]
# 
# jobs:
#   build_wheels:
#     strategy:
#       matrix:
#         os: [ubuntu-latest, windows-latest, macos-latest]
#     runs-on: ${{ matrix.os }}
# 
#     steps:
#       - uses: actions/checkout@v3
#         
#       - uses: pypa/cibuildwheel@v2.14
# 
#       - uses: actions/upload-artifact@v3
#         with:
#           path: ./wheelhouse/*.whl
# ```
# ---
# 

# ## So much more
# 
# Some examples of classes:
# 
# ```python
# #include <pybind11/operators.h>
# 
# using namespace pybind11::literals;
# 
# PYBIND11_MODULE(example, m) {
#     py::class_<Vector>(m, "Vector")
#         .def(py::init<double, double>())
#         .def_property("x", &Vector::getX, &Vector::setX)
#         .def_property("y", &Vector::getY, &Vector::setY)
#         .def("mag", &Vector::mag, "I am a mag function")
#     
#         .def("unit", [](const Vector& self){return self.unit();})
#     
#         .def("__str__", [](const Vector& self){return py::str("[{}, {}]").format(self.getX(), self.getY());})
#         
#         .def(py::self *= float())
#         .def(float() * py::self)
#         .def(py::self * float())
# }
# ```

# You can use lambda functions almost anywhere, and you can ask for `py::object` or the C++ type interchangeably, or cast between them.