Category Archives: CS101

Iteration versus Recursion

19 Monday Dec 2016

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When it comes to what makes a computer (or any other) language a programming language, there are three characteristics usually required:

  1. Saving state (variables)
  2. Selecting a code path (if-then)
  3. Iteration or recursion (or equivalent)

This post is just a brief note (for a friend) about the third item and why it allows three distinct options.

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The Thing About Constants

16 Tuesday Aug 2016

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Along with “always use less-than” is another great piece of always advice, except this one is a prohibition, a never rather than an always (same thing, really, from a programmer’s point of view).

It has to do with never having literal values embedded in your code!

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Counting From Zero

08 Monday Aug 2016

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In his brief 1982 essay (EWD831), computer science giant Edsger Dijkstra examines a topic that (inappropriately, as it turns out) vexes some programmers: Why in the world do computer people count starting at zero? Everyone knows that counting starts at one!

As it turns out, there are two very good reasons for counting from zero!

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State Engines, part 3

25 Wednesday Nov 2015

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In the first two parts of this series I’ve introduced state engines and taken apart a specific instance of an engine. Now it’s time to tie together the design idea with approaches to building a variety of such engines.

Because the programming logic is in the state table, the engine can be fairly generic. That means it’s possible to create a state engine framework you can reuse for a variety of applications.

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State Engines, part 2

11 Wednesday Nov 2015

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Last time I introduced state engines and state tables. I showed parts of a simple implementation of one in Python. It parsed the language introduced in Little Programming Languages. This post continues that, so be sure you’ve read that first article.

I got as far as the state table implementing the process, and that’s where this post picks up. I’ll also get into the SourceReader class that does the heavy lifting.

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State Engines, part 1

08 Sunday Nov 2015

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At one point in my career, the state engine (SE) was one of my favorite AWK hammers. At the time much of the work involved text processing or, in some cases, serial byte processing (which is not quite the same thing). That sort of thing is right in the wheelhouse for a state engine.

They are a very useful tool and an important part of any programmer’s toolkit.

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Rule #4: Comment As You Go!

05 Monday Oct 2015

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There is a common tendency, as we crank out code, to think that we’ll come back later and write some really good comments — comments that future reviewers will view with admiration for their clarity, completeness, and humor. But if we’re honest we have to admit: Later never comes. We never go back and write those great comments. Often we don’t write any comments at all other than some placeholder we might dash off at the time.

Which is why Rule #4: Comment As You Go!

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HTML is not a programming language!

22 Monday Dec 2014

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A webpage is a text document written in HTML. This document may also contain CSS and/or JavaScript, but it’s basically an HTML text document. You could write one — including the CSS and JavaScript — using just a pencil and paper.

Despite not needing a computer to write, all three are computer languages — they are languages used by, understood by, computers (and trained humans). However only one of those (JavaScript) is a programming language.

This is a brief explanation of which is which and why.

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Getting to the Next Hill

23 Monday Jun 2014

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Last week I took my car in for scheduled service, and when I asked how long it might take, the guy said it was specified as one-and-a-half hours of labor. He could do that because there are thousands upon thousands of data points where a competent mechanic has performed that exact service, so there is a very clear idea how long it takes.

But ask a researcher how long it will take to find what they’re looking for, and the answer is usually, “I have no idea. I’ll know after I find it.” The path a researcher follows is usually new and unexplored, so it’s impossible to predict how long the path actually is.

Creating new software is much more like research than auto service, because it involves traveling unknown ground. Despite this, software development managers often act as if new development is predictable.

It often isn’t!

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