A Jupyter kernel for C++ based on the C++ interpreter cling and the native implementation of the Jupyter protocol xeus.

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Introduction

xtensor is a C++ library meant for numerical analysis with multi-dimensional array expressions.

xtensor provides

an extensible expression system enabling lazy broadcasting.
an API following the idioms of the C++ standard library.
tools to manipulate array expressions and build upon xtensor.

The implementation of the containers of xtensor is inspired by NumPy, the Python array programming library. Adaptors for existing data structures to be plugged into our expression system can easily be written. In fact, xtensor can be used to process numpy data structures inplace using Python's buffer protocol.

xtensor requires a modern C++ compiler supporting C++14. The following C+ compilers are supported:

On Windows platforms, Visual C++ 2015 Update 2, or more recent
On Unix platforms, gcc 4.9 or a recent version of Clang

Usage

To run the selected code cell, hit

Shift + Enter

Output and error streams

std::cout and std::cerr are correctly redirected



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#include <iostream>

std::cout << "some output" << std::endl;



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std::cerr << "some error" << std::endl;



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#include <stdexcept>



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throw std::runtime_error("BAAAD");

Omitting the ; in the last statement of a cell gives an output



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int i = 4



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int j = 5;



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j

Interpreting the C++ programming language

cling has a broad support of the features of C++. You can define functions, classes, templates, etc ...

Functions



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double sqr(double a)
{
    return a * a;
}



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double a = 2.5;
double asqr = sqr(a);
asqr

Classes



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class Foo
{
public:

    virtual ~Foo() {}
    
    virtual void print(double value) const
    {
        std::cout << "Foo value = " << value << std::endl;
    }
};



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Foo bar;
bar.print(1.2);

Polymorphism



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class Bar : public Foo
{
public:

    virtual ~Bar() {}
    
    virtual void print(double value) const
    {
        std::cout << "Bar value = " << 2 * value << std::endl;
    }
};



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Foo* bar2 = new Bar;
bar2->print(1.2);
delete bar2;

Templates



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#include <typeinfo>

template <class T>
class FooT
{
public:
    
    explicit FooT(const T& t) : m_t(t) {}
    
    void print() const
    {
        std::cout << typeid(T).name() << " m_t = " << m_t << std::endl;
    }
    
private:
    
    T m_t;
};

template <>
class FooT<int>
{
public:
    
    explicit FooT(const int& t) : m_t(t) {}
    
    void print() const
    {
        std::cout << "m_t = " << m_t << std::endl;
    }
    
private:
    
    int m_t;
};



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FooT<double> foot1(1.2);
foot1.print();



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FooT<int> foot2(4);
foot2.print();

C++11 / C++14 support



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class Foo11
{
public:
    
    Foo11() { std::cout << "Foo11 default constructor" << std::endl; }
    Foo11(const Foo11&) { std::cout << "Foo11 copy constructor" << std::endl; }
    Foo11(Foo11&&) { std::cout << "Foo11 move constructor" << std::endl; }
};



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Foo11 f1;
Foo11 f2(f1);
Foo11 f3(std::move(f1));



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#include <vector>

std::vector<int> v = { 1, 2, 3};
auto iter = ++v.begin();
v



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*iter

... and also lambda, universal references, decltype, etc ...

Documentation and completion



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?std::vector

Using the `display_data` mechanism



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#include <string>
#include <fstream>

#include "xtl/xbase64.hpp"



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std::ifstream fin("images/marie.png", std::ios::binary);
std::stringstream buffer;
buffer << fin.rdbuf();



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xeus::xjson mime;
mime["image/png"] = xtl::base64encode(buffer.str());



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xeus::get_interpreter().display_data(
    std::move(mime),
    xeus::xjson::object(),
    xeus::xjson::object());



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std::ifstream fwav("audio/audio.wav", std::ios::binary);
std::stringstream wav_buffer;
wav_buffer << fwav.rdbuf();
xeus::xjson audio_mime;



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audio_mime["text/html"] =
    std::string("<audio controls=\"controls\"><source src=\"data:audio/wav;base64,")
    + xtl::base64encode(wav_buffer.str()) +
    "\" type=\"audio/wav\" /></audio>";



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xeus::get_interpreter().display_data(
    std::move(audio_mime),
    xeus::xjson::object(),
    xeus::xjson::object());



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