Nim cell magic for Jupyter and JLab Notebooks

nim_magic.py

"""
nim_magic.py
Jupyter cell magic for your favorite programming language.

This is now also available as a proper repo:
https://github.com/apahl/nim_magic

All further changes will be tracked there.

Requirements: Nim (https://nim-lang.org), nimpy (`nimble install nimpy`, thanks to @yglukhov for this great library!)

Just put this file in some Python import dir

and then, in a Jupyter or JLab Notebook:

In [1]:
    %load_ext nim_magic


In [2]:
    %%nim -d:release
    proc greet(name: string): string {.exportpy.} =
        return "Hello, " & name & "!"


In [3]:
    greet("World")


In [4] (this will remove temporary dirs created by nim_magic):
    %nim_clear


CHANGES: All symbols from the extension module are now imported 
    into the current namespace.
    This was necessary to enable re-import after recompilation.
    To achieve this, each compiled module gets an arbitrary new name.
    All generated files are now put in the dir `nimmagic`.
    This dir can be removed manually or with the special line magic command: `%nim_clear`in a Notebook cell

"""

import os
import shutil
import sys
import time
import subprocess as sp
from IPython.core.magic import (Magics, magics_class, 
                                line_magic, cell_magic)


@magics_class
class NimMagics(Magics):

    @line_magic
    def nim_clear(self, cmd):
        """%nim_clear
        will remove the temporary dirs used by nim_magic."""
        
        shutil.rmtree('nimmagic', ignore_errors=True)
        print("Removed temporary files used by nim_magic.")

    @cell_magic
    def nim(self, options, code):
        """`options` can be left empty or contain further compile options, e.g. "-d:release" 
        (separated by space).
        
        Example:
        
        %%nim -d:release
        <code to compile in release mode>"""
        
        if not os.path.isdir("nimmagic"):
            os.mkdir("nimmagic")

        glbls = self.shell.user_ns
        name = time.strftime("nim%y%m%d%H%M%S")
        code = "import nimpy\n\n" + code
        ext = "pyd" if sys.platform.startswith('win') else "so"
        open("nimmagic/{}.nim".format(name), "w").write(code)
        cmd = "nim {1} --hints:off --app:lib --out:nimmagic/{0}.{2} c nimmagic/{0}.nim".format(name, options, ext)
        cp = sp.run(cmd, shell=True, check=False, encoding="utf8", stdout=sp.PIPE, stderr=sp.PIPE)
        print(cp.stderr)
        if cp.returncode == 0:
            import_exec = "from nimmagic.{} import *".format(name)
            exec(import_exec, glbls)


def load_ipython_extension(ipython):
    ipython.register_magics(NimMagics)