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HrisShterevHrisShterev
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Add cpp notebooks and CI to check them (#7)
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‎xeus-cpp/01_verification.ipynb‎

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{
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"cells": [
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{
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"cell_type": "markdown",
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"id": "333cda22-5985-44ed-9bcc-5f34378c1bec",
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"metadata": {},
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"source": [
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"# Environment setup and basic verification\n",
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"\n",
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"---"
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]
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},
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{
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"cell_type": "code",
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"execution_count": 1,
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"id": "884a03ad-230a-4725-90fd-939990e123da",
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"metadata": {},
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"outputs": [
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{
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"name": "stdout",
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"output_type": "stream",
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"text": [
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"C++ Version: 202302\n",
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"42\n"
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]
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}
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],
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"source": [
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"#include <iostream>\n",
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"\n",
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"std::cout << \"C++ Version: \" << __cplusplus << std::endl; //Checks C++ version\n",
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"\n",
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"int a = 10;\n",
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"int b = 32;\n",
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"std::cout << a + b << std::endl;\n",
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"//Conducts a basic mathematical operation\n",
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"//Checks kernel responsiveness"
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]
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}
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],
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"metadata": {
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"kernelspec": {
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"display_name": "C++23",
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"language": "cpp",
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"name": "xcpp23"
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},
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"language_info": {
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"codemirror_mode": "text/x-c++src",
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"file_extension": ".cpp",
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"mimetype": "text/x-c++src",
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"name": "C++",
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"version": "23"
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}
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},
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"nbformat": 4,
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"nbformat_minor": 5
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}

‎xeus-cpp/02_persistence.ipynb‎

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{
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"cells": [
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{
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"cell_type": "markdown",
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"id": "bbff0978-540f-4307-96fb-6a4692e4fd4d",
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"metadata": {},
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"source": [
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"# State persistence across cells in xeus-cpp\n",
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"\n"
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]
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},
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{
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"cell_type": "markdown",
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"id": "35740592-c29e-4c7b-87e8-52cc0060cd59",
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"metadata": {},
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"source": [
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"#### In a standard C++ development invironment, each time you run a program, the memory is allocated, the `main()` function executes, and then the memory is completely wiped. In **xeus-cpp**, the execution model is **persistent**\n",
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"\n",
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"---"
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]
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},
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{
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"cell_type": "markdown",
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"id": "ed28c993-b195-4eb1-85cc-fee63cb04470",
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"metadata": {},
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"source": [
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"\n",
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"### What is state persistence?\n",
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"\n",
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"The Jupyter notebook acts as a single, ongoing C++ session. When you execute a cell, the kernel compiles that specific snippet and integrates it into the current process memory. This means, that any variable, function or object defined in a cell remains alive and accessible in any other cell.\n",
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"\n",
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"***NB! The order in which you run cells matters. Running cells out of order can cause errors and unexpected behaviour***"
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]
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},
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{
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"cell_type": "markdown",
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"id": "b493b694-04f1-4a01-997f-ceb4ef8d1499",
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"metadata": {},
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"source": [
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"\n",
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"### The following program demonstrates how state persistence in xeus-cpp works exactly:"
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]
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},
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{
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"cell_type": "code",
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"execution_count": 1,
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"id": "b2d303a7-96ee-4aeb-8c84-4884bba161f6",
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"metadata": {},
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"outputs": [],
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"source": [
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"int counter = 0;"
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]
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},
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{
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"cell_type": "code",
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"execution_count": 2,
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"id": "d541cb78-b2ae-4175-b9ae-a76014a37e28",
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"metadata": {},
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"outputs": [],
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"source": [
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"#include <iostream>\n",
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"\n",
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"void inc()\n",
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"{\n",
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" counter++;\n",
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" std::cout << \"Current Value: \" << counter << std::endl;\n",
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"}"
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]
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},
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{
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"cell_type": "code",
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"execution_count": 3,
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"id": "d2c38c70-3e92-446a-8c10-1c62edf177e1",
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"metadata": {},
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"outputs": [
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{
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"name": "stdout",
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"output_type": "stream",
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"text": [
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"Current Value: 1\n"
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]
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}
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],
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"source": [
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"inc(); //Run this cell multiple times to see persistence in action"
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]
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}
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],
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"metadata": {
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"kernelspec": {
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"display_name": "C++23",
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"language": "cpp",
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"name": "xcpp23"
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},
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"language_info": {
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"codemirror_mode": "text/x-c++src",
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"file_extension": ".cpp",
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"mimetype": "text/x-c++src",
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"name": "C++",
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"nbconvert_exporter": "",
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"pygments_lexer": "",
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"version": "cxx23"
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}
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},
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"nbformat": 4,
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"nbformat_minor": 5
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}

‎xeus-cpp/03_redefinition.ipynb‎

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{
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"cells": [
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{
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"cell_type": "markdown",
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"id": "d7a1b687-3743-4786-84b0-71b6eed7d62e",
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"metadata": {},
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"source": [
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"# Testing redefinition behaviour\n",
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"\n",
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"\n",
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"#### In a traditional C++ workflow, you write code in a `.cpp` file, compile it all at once, and run it. If you want to change a variable type, you simply edit the file and recompile. However, **xeus-cpp**'s cell-based workflow enables several workarounds\n",
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"---"
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]
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},
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{
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"cell_type": "markdown",
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"id": "96f3d068-6433-472a-a4b7-02f253a22600",
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"metadata": {},
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"source": [
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"In this example, we declare a variable with an `int` type, which we will name `a`, and assign a value to it"
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]
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},
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{
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"cell_type": "code",
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"execution_count": 1,
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"id": "216e746c-4eae-4655-a18d-8e1fb6da4327",
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"metadata": {},
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"outputs": [
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{
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"name": "stdout",
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"output_type": "stream",
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"text": [
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"Initial declaration: 100\n"
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]
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}
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],
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"source": [
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"#include <iostream>\n",
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"\n",
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"int a = 100;\n",
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"std::cout << \"Initial declaration: \" << a << std::endl;"
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]
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},
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{
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"cell_type": "markdown",
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"id": "991adb4c-e105-4f58-8b5d-1147c2ac8d6d",
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"metadata": {},
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"source": [
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"Next, we try to redeclare the variable, this time to `double`, and assign a new value to it"
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]
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},
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{
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"cell_type": "code",
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"execution_count": null,
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"id": "54d35e14-c256-4692-8a7c-f5b7e3815030",
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"metadata": {},
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"outputs": [],
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"source": [
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"double a = 55.5;\n",
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"std::cout << \"New declaration: \" << a << std::endl;"
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]
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},
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{
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"cell_type": "markdown",
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"id": "df0fdee0-4747-4ba9-b242-76d8c870cdc5",
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"metadata": {},
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"source": [
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"This action of redefinition is **illegal** in standard C++, because the variable `a` already exists as an `int`.\n",
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"\n",
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"Two workarounds exist:\n",
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"- overwriting the value **without redeclaring the type**\n",
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"- creating a temporary \"bubble\" by redeclaring it in a **different scope**, so the variables don't interfere. This method doesn't change the value or the type of the global variable\n",
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" \n",
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"***NB!*** It is advised that unless you absolutely must use the same name for a variable, you simply pick a new name"
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]
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},
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{
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"cell_type": "markdown",
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"id": "f52dad1c-3374-438b-9e6f-50e19470a057",
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"metadata": {},
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"source": [
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"---\n",
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"\n",
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"### First method - overwriting the value"
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]
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},
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{
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"cell_type": "code",
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"execution_count": 4,
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"id": "0a466dd1-9301-4bd0-a981-491c7906ba8f",
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"metadata": {},
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"outputs": [
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{
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"name": "stdout",
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"output_type": "stream",
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"text": [
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"Updated value: 20\n"
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]
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}
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],
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"source": [
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"a = 20.8;\n",
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"std::cout << \"Updated value: \" << a << std::endl;"
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]
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},
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{
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"cell_type": "markdown",
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"id": "90a1c883-bb3a-402f-bb12-d6aaa4f886db",
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"metadata": {},
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"source": [
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"When using the first method to assign a floating point value to an `int`, the new value is floored to the closest integer\n",
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"\n",
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"As shown in this example \n",
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"\n",
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"> 20.8 --> 20"
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]
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},
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{
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"cell_type": "markdown",
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"id": "87b8d709-e706-4edd-888a-6d0a6a788b8a",
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"metadata": {},
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"source": [
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"### Second method - redeclaring in a different scope"
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]
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},
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{
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"cell_type": "code",
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"execution_count": 6,
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"id": "0c765722-7a41-4b25-92df-c10dea32f5e3",
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"metadata": {},
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"outputs": [
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{
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"name": "stdout",
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"output_type": "stream",
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"text": [
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"Updated value (scoped): 12.34\n",
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"Global value: 20\n"
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]
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}
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],
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"source": [
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"{\n",
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" float a = 12.34f; //safe because it's inside a local scope\n",
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" std::cout << \"Updated value (scoped): \" << a << std::endl;\n",
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"}\n",
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"\n",
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"//Outside the brackets, the original int still exists\n",
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"std::cout << \"Global value: \" << a << std::endl;"
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]
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}
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],
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"metadata": {
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"kernelspec": {
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"display_name": "C++23",
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"language": "cpp",
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"name": "xcpp23"
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},
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"language_info": {
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"codemirror_mode": "text/x-c++src",
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"file_extension": ".cpp",
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"mimetype": "text/x-c++src",
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"name": "C++",
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"version": "23"
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}
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},
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"nbformat": 4,
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"nbformat_minor": 5
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}

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