Learn Nim with Python (from the beginning of the year).

One of the features of the compilation language Nim (formerly Nimrod)

Formerly Nimrod, Nim, which has been under development since around 2008. To get Python users to understand its features, I think it's a good idea to take a look at the following code in the Japanese version of wikipedia, nim.

wikipedia.nim

proc reverse(s: string): string =
  result = "" #Implicit result variable
  for i in countdown(high(s), 0):
    result.add s[i]

var str1 = "Reverse This!"
echo "Reversed: ", reverse(str1)

A little bit of wikipedia commentary:

--Focus on the implicit result variable. In Nim, procedures whose return type is not void have an implicit result variable. The result variable holds the return value of the procedure. --countdown in a for loop is an iterator. Here, an iterator that counts down from the character string length obtained by high (s) to 0 is described.

Although Nim is a typed compilation language, it can be written like a scripting language.

It seems that Nim began to be known in Japan around the blog about five years ago by Takano32, "Let's write FizzBuzz with Nimrod!".

• http://takano32.blogspot.jp/2011/12/nimrod-fizzbuzz.html

Takano32, a Ruby committer, then immediately posted an entry, "How can I use Python with Nimrod !?"

• http://takano32.blogspot.jp/2011/12/nimrod-python.html

Yes, there are quite a few people trying to use python and nim together (what about the relationship between ruby and nim?).

So, this time, I'd like to call nim from python and think about how to use it.

Call nim from python.

Basically, if you follow Connecting Nim to Python, it's quick. What we are doing is creating a so-called shared library in C language from the source code of nim. Binaries are execution environment dependent. Below is an example on a Mac. If you have xcode and the latest brew, you only need to install nim as follows.

brew install nim

First, prepare nim code with only one procedure (function),

fn1.nim

proc summer*(x, y: float): float {. exportc, dynlib .} =
  result = x + y

Below, it will be made into a shared library.

nim c --app:lib fn1.nim

The python code that calls the generated libfn1.dylib is below (using the python 2.7 that comes with the Mac from the beginning): Since it is a C language shared library call, use ctypes.

py2nim1.py

from ctypes import *

def main():
    test_lib = CDLL('./libfn1.dylib')

    # Function parameter types
    test_lib.summer.argtypes = [c_double, c_double]

    # Function return types
    test_lib.summer.restype = c_double

    sum_res = test_lib.summer(1.0, 3.0)
    print('The sum of 1.0 and 3.0 is: %f'%sum_res)

if __name__ == '__main__':
    main()

If you pay attention to the double type in the 64-bit environment, you can get the answer "4.0" from nim.

Is it used, for example, in-house batch processing system?

In an environment where numpy, pypy, micropython, R18python ... etc. are not obscene and specialized py terms are used in pursuit of execution speed, nim may be able to blend in smoothly. Even if it doesn't, "Hey, look at this, you. What do you think of this guy? ”-If you have an environment like“ It's really big ... (in terms of computational power) ”, it's possible to challenge the process with python + C language + nim. It seems to be.

Since about 20 years when it was a minor language, innumerable code has been written by fierce men, and there are various "arts" in python. For example, the Mac environment contains an Objective-c (++) calling library called PyObjC, and you can immediately call nim while calling a GUI written in Objective-c with python. Since the GUI call description on the python side is long, put the code in gist.

• https://gist.github.com/kmry/d876ea7995978eecddea09bda0244316

Execution example:

Creating a GUI for users to call a calculation library written in nim is much easier with python. Nim, the compilation language, can concentrate on data processing descriptions that call C / C ++, which has a high affinity, as appropriate.

Continue

... and I wrote about the ratio and common sense about nim, which is now limited to the material language. But, big brother, don't worry. With this as a starting point, I will write a story post on the subject of IoT in the near future.