{
 "metadata": {
  "name": "9932_06_02"
 },
 "nbformat": 3,
 "nbformat_minor": 0,
 "worksheets": [
  {
   "cells": [
    {
     "cell_type": "markdown",
     "metadata": {},
     "source": [
      "Chapter 6, example 2\n",
      "====================\n",
      "\n",
      "In this example, we show how to create a simple IPython extension that allows to write and evaluate C++ code directly in the notebook.\n",
      "\n",
      "The `cppmagic.py` script contains the following code:\n",
      "\n",
      "    import IPython.core.magic as ipym\n",
      "    \n",
      "    @ipym.magics_class\n",
      "    class CppMagics(ipym.Magics):\n",
      "        @ipym.cell_magic\n",
      "        def cpp(self, line, cell=None):\n",
      "            \"\"\"Compile, execute C++ code, and return the standard output.\"\"\"\n",
      "            # Define the source and executable filenames.\n",
      "            source_filename = 'temp.cpp'\n",
      "            program_filename = 'temp.exe'\n",
      "            # Write the code contained in the cell to the C++ file.\n",
      "            with open(source_filename, 'w') as f:\n",
      "                f.write(cell)\n",
      "            # Compile the C++ code into an executable.\n",
      "            compile = self.shell.getoutput(\"g++ {0:s} -o {1:s}\".format(\n",
      "                source_filename, program_filename))\n",
      "            # Execute the executable and return the output.\n",
      "            output = self.shell.getoutput(program_filename)\n",
      "            return output\n",
      "    \n",
      "    def load_ipython_extension(ipython):\n",
      "        ipython.register_magics(CppMagics)\n"
     ]
    },
    {
     "cell_type": "markdown",
     "metadata": {},
     "source": [
      "We load the extension as if it was a simple Python module. The `load_ipython_extension` function is called with the IPython interpreter instance as an argument."
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "%load_ext cppmagic"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [],
     "prompt_number": 1
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "cpp?"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [],
     "prompt_number": 2
    },
    {
     "cell_type": "markdown",
     "metadata": {},
     "source": [
      "We now have access to the `cpp` cell magic, which allows to write C++ code in the notebook, compile it, execute it, and return the result."
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "%%cpp\n",
      "#include<iostream>\n",
      "int main()\n",
      "{\n",
      "    std::cout << \"Hello world!\";\n",
      "}"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "output_type": "pyout",
       "prompt_number": 3,
       "text": [
        "['Hello world!']"
       ]
      }
     ],
     "prompt_number": 3
    }
   ],
   "metadata": {}
  }
 ]
}