Sunday, February 15, 2015

Customs in Coding Style

"What's in a name? That which we call a rose
By any other word would smell as sweet.
So Romeo would, were he not Romeo called,
Retain that dear perfection which he owes
Without that title. Romeo, doff thy name;
And for thy name, which is no part of thee,
Take all myself.
-- Shakespeare, Romeo and Juliet
Act II, Scene II, Lines 43-49.1

Recently for a lunch and learn at work my team re-watched Clean Coders episode 2: Names++.  As with all Uncle Bob videos I highly recommend it.  Being a developer who programs a bit in C# I do have to disagree with his statements about bucking the convention of starting interfacing with an "I", the example he gives is IAccount vs Account.  I agree with most of what he said and having programed in many other language I completely agree that the "I" does not add any additional information but I still use it when I program in C#.  Why?

"Pindar was right, in my judgment, when he said, '[Custom] is the king [over] all.' "
-- Herodotus, The Histories
Translated by George Rawlinson
Book III

Custom is king of all.  I strongly believe that if there is a current naming standard in a language you should just follow it.  When I am doing C# in Visual Studio whatever ctrl+k ctrl+d does is the standard I follow (for the most part).

Why?  Source code is for humans to read and understand, all groups, peoples, languages, ... have customs.  These customs are often built into the communications patterns that are followed and are implied by parties taking part in the communication.

Do not believe me, how would I order a Coca-Cola where you are from?  I grew up in the Chicago area, my whole life people referred to all soft-drinks as pop.  I currently work in Milwaukee guess what they call soft-drinks?  In Milwaukee a soft-drink is called soda.  As a kid I vacationed in the Ozarks, what do you think they would call a soft-drink?  All soft-drinks in the southern part of Ozarks were referred to as coke.  There is a whole website which covers all this pop VS soda VS coke.

What is my point?  When coding in a language if you want other people who program in that language to understand what your code is doing with the minimal amount of effort you should just follow the existing standards of the language you are coding in.

There are lots of other place in software development to have a style and flair, bucking current language naming standards is not the place to do it.

"[I]f one were to offer men to choose out of all the customs in the world such as seemed to them the best, they would examine the whole number, and end by preferring their own; so convinced are they that their own usages far surpass those of all others."
-- Herodotus, The Histories
Translated by George Rawlinson
Book III

Sunday, February 8, 2015

The LISP Connection

"There is a history in all men's lives"
-- Shakespeare, Henry IV Part 2
Act III, Scene I, Line 76

Questions not asked

Why are there so many conference sessions about things to come and how things will get better?

Why are there so many blog posts about what is new and the 5 to 10 things you should know about them?

How many sessions are there that reflect upon the past and what we've learned along the way?

How many blog posts are there about the history of programming and the important lessons we've learned along the way?

What I like about Lisp

LISt Processing is one of the oldest computer languages (FORTRAN is older by a year).  Using LISP or one of its dialects you feel a connection to those programmers and scientist that came before you.

Randall Munroe's xkcd, Lisp Cycles

This sense of connection is an old but very important idea.

What Lisp has taught me thus far

Over the past few months I've been learning Clojure from the Joy of Clojure and now Programming Clojure, here are the things I've learned thus far:

  • homoiconic leads to fewer syntax errors and easier to read code
  • compose functionality from smaller well tested functionality
  • separate assignment of values from actions upon values
I look forward to continuing my path along the Lisp way.

Unlikely credits

Questions not asked and titled inspired by the Rainbow Connection, written by Paul Williams.

Sunday, February 1, 2015

Reducing Filter to Reduce OR All You Need is Fold

"All springs reduce their currents to mine eyes"
-- Shakespeare, Richard III
Act II, Scene II, Line 68


Last time we look at using the ideas presented in Graham Hutton's paper "A tutorial on the universality and expressiveness of fold" around mapping map to a fold.  This post will look at filtering filter down to a fold.


Filter goes by many different names, to those who speak Clojure, Haskell, and Underscore.js it is called Filter, to others that speak C# it is know as Where, while those that speak C++ know it as Remove, ... we could go on like this for a bit.

The point is that this is the same idea called by different names.  With a Filter what you are doing is taking a collection and applying a predict which state which members of the collection to let into the resulting collection and which members to not allow.  Think of it as a bouncer at a club, some of the people looking to get in will be admitted to the club others will be turned away, the bouncer is the predict, the people are the collection, and those few that get into the club are the resulting collection.

An easy example is to filter out all members of a collection of integers which are not odd.  In Clojure and C# we could use the following code to do this.

We see in both languages that we can use a higher order function to filter our collection down to the resulting collection with the property of oddness that we are looking for.  Clojure has a built in predicate function to check for oddness of a number while in C# we have to roll our own with a lambda function.


We talk about Fold last time, but we'll review it really quick.

When we are talking about Fold we are talking about taking a collection and applying a function against each member of the collection resulting in a result of a single "value".

Hmm, this sounds kind of similar to what we are doing with Filter...

Folding Filter into a Fold

When we looked at Filter we saw some similarities to Fold.

  1. apply a function to each member of a collection
  2. building a result

In fact we could look at Filter in the following way:

If we take a Fold (aka Reduce), a predicate function, and a collection to hold the resulting collection, we end up with a Filter.  We can looking at the following examples in Clojure and C# using our friend isOdd with a Fold to produce a Filter

In the Clojure code we see that we have a predicate function testing if a value is odd and if it is we conj it to a memorized resulting collection else we just pass along the memorized result collection.  We seed the Reduce (aka Fold) with an empty vector was is used to hold the memorized result collection.  Note, the memorized result collection is %1 in the lambda function while the current member we are looking at is %2, this pattern is typical in Folds across different languages (I cannot think of one which does not have this as the order, but maybe one exist).

In the C# code we new up a List to hold our resulting collection and in our lambda we test the current member we are looking at, if it passes we add it to the memorized result collection, then we always pass the memorized result collection along to the next call of Aggregate (aka Fold).  Since we had an array of integers as our input, we need to reshape the result collection with a call to ToArray.

By looking at this simple example we see that all we really need is Fold.  :)