FlowSharpCode, continued…

fsc2.png

A simple example, but the “problem” is that the three Drakon shapes (begin loop, output, and end loop) each still have individual C# code-behind in each shape.  For example, the begin loop has the code-behind:

 var n in Enumerable.Range(1, 10)

My original idea was that the Drakon shape description should not define the language-specific syntax, instead that should be implemented by the developer in the code-behind.

In practice (and I’ve written a complex application in FlowSharpCode, so I know) it becomes unwieldy to deal with one-liner code behind, the result of which is that I tend not to use Drakon shapes, but that results in nothing better than a meaningless box with some code in it.

I’m also reluctant to put the code in the shape label (though this is supported) as again we’re now dealing with language specific syntax.

I’m also reluctant to create a meta-language for Drakon shapes, for example, something that could interpret:

n = 1..10

into C#, Python, whatever.  What if the developer wants to write:

Count from 1 to 10

So, what I’m considering is letting the developer create the Domain Specific Language (DSL) so that they can expressively communicate the semantics of a Drakon shape and also provide the rules for how the semantics is parsed, ideally in an intermediate language (IL), for example, something that expresses a for loop, a method call, whatever.

The advantage to this is that the developer can create whatever DSL they like to work in, the IL glues it together into the concrete language.

Two things happen then:

  1. The DSL is interchangeable.  Any IL can be super-composed into your DSL choice.
  2. The IL is language independent, so it can be de-composed into language specific syntax.

Item #2 of course imposes some significant limitations — what if a language doesn’t support classes, or interfaces, or yield operator, or whatever?  I’m not particularly too concerned about that as a language-independent DSL/IL is more of a curiosity piece, as it becomes rapidly untenable when your code starts calling language-framework-platform dependencies.

However, I’d love to hear my readers thoughts on this DSL/IL concept I’m considering.

 

 

FiddleDock – Creating a Dockerized Python Fiddle Web App

fiddledock.png

 

Using C#, a simple web server, and Docker, I’ve been putting together an example of one approach for how to create a “Fiddle” web app to run Python (or other script languages) in a Docker container.

The source code can be found on GitHub, but beware that at the time of this writing, the implementation isn’t complete (only “Run on Docker” and “Run on Host” buttons do anything) and I’m in the midst of writing the article on how I put this together (also in that repo – watch the progress as I write the article and finish the web app!)

Code Iterations – A Mentoring Example

refactoring.jpg

One of the pleasures in life is mentoring another developer, particularly when the other developer is smart and motivated to learn.  This article, on populating a tree from a collection of paths, was the result of some weekend prep work and is a good case study on refactoring.  By going through the process myself and documenting it, I was able to present the problem in general terms, and the person I was mentoring did the heavy mental lifting with only occasional guidance on my part.  This worked because I was prepared — had I not done this prep work, I would have taken away from my mentee’s experience to  actually solving the problem himself.

Article here.

Two Articles Win First Prize for March

firstplace.jpg

Well, that was a “first!” — Two articles:

Understanding Merkle Trees

Full Duplex Asynchronous Read/Write with Named Piped

have won first place in Code Project‘s monthly article competition in the categories of “Best Everything Else” and “Best C# Article” for the month of March 2017.

And as always, with great appreciation to the amazing people @codeproject who have made Code Project possible!

 

Who was Born on Your Birthday?

cupcake2.jpg

Six lines (not including imports) of Python code to scrape the website onthisday.com for the “persons of interest.”  Impressive!

Package dependencies:

pip install lxml
pip install cssselect
pip install requests

The Python code:

import requests
from lxml import html
from lxml.cssselect import CSSSelector
from lxml import etree
 
page = requests.get("http://www.onthisday.com/birthdays/august/19")
tree = html.fromstring(page.content)
sel = CSSSelector('.section--person-of-interest')
pois = sel(tree)
 
for poi in pois:
 poi.xpath("div/div/div[1]/p")[0].text_content()

The results (for my birthday):

'1871 Orville Wright, aviator (Wright Brothers), born in Dayton, Ohio (d. 1912)'
'1878 Manuel Luis Quezon y Molina, Second President of the Philippines (1935-42), born in Baler, Aurora, Philippines (d. 1944)'
'1919 Malcolm Forbes, American publisher of Forbes Magazine, born in Brooklyn, New York (d. 1990)'
'1946 Bill Clinton [William Jefferson], 42nd US President (Democrat, 1993-2001), born in Hope, Arkansas'
'1967 Satya Nadella, Indian-American businessman (CEO of Microsoft), born in Hyderabad'