Exercises in Programming Style–Pipeline

NOTE : read the rest of the series, or check out the source code.

If you enjoy read­ing these exer­cises then please buy Crista’s book to sup­port her work.

exercises-prog-styles-cover

Fol­low­ing on from the last post, we will look at the Pipeline style today.

 

Style 5 – Pipeline

Although Crista has called this the Pipeline style, you would recognize it as Functional Programming.

Constraints

  • Larger problem is decomposed using functional abstraction. Functions take input, and produce output
  • No shared state between functions
  • The larger problem is solved by composing functions one after the other, in a pipeline

 

Finally we’re able to write some idiomatic F# code!

 

Functions

The structure of the application is identical to that of the procedural style we explored in the last post. Except, this time around we’ll be passing data around as input and output, rather than global shared state.

image

and then to tie everything together:

image

 

Conclusions

You might notice that the above code is actually very similar to what we had in the procedural style. By removing the use of shared state our functions are now idempotent and provide better encapsulation.

Finally, compared to Crista’s solution in Python:

image

the beauty of F#’s pipes (|>) idiom really shone through.

 

You can find all the source code for this exer­cise here.

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