Sunday, October 20, 2013

Test-Assisted Design

I'm re-thinking my opinions about unit tests and test-driven design. On the one hand, part of me immediately liked the idea of TDD as soon as I heard it: by writing out your tests first, you have a clear, unambiguous spec for what you're supposed to build. It's clear, because it has to be a test that the machine can run, and it's unambiguous because it's a test. It either passes or it doesn't.

On the other hand, I've been having second thoughts about unit tests ever since I saw Rich Hickey's talk on Simple Made Easy, the Magna Carta of functional programmers. Tests are good, but-- Tests are necessary, but--

The thing is, unit tests could be thought of as a kind of code smell, or a kind of technical debt. You're writing tests because you don't know what your code is going to do. And maybe that's unavoidable. Maybe programming is just too complicated for us to write code that always does exactly what we expect it to do. But still, a code smell, a sign of an undesirable circumstance that we should be trying to avoid or reduce.

Monday, July 29, 2013

Nil is not enough

Here's the context: I'm separating out all my data-store-related functions into their own namespace. Specifically, I'm working on my User model. I want to write a function that creates a new user in my data store, but only if there's not already a user with the same username. No problem, right? If the user already exists, I just return nil, the same as for any other error.

Now I'm using the create-user function I wrote above, and I pass in a user name, and I get back nil. Does that mean there was a database error (not enough space left on drive) or does that mean there was already a user with the same name? I want to get additional information out of nil, but nil doesn't contain any information. It's nil!

Sunday, July 21, 2013

Setting up Friend: a few preliminaries

[Revised: found out my first diagnosis and fix were incorrect, but eventually I tracked down the real answers.]

For my summer project, I'm developing a web site that local food banks can use to let people know what items they currently need. Long term, I want this to be accessible via smart phones, but for now I'm just getting started with the basics. I'm using the Luminus framework to kick things off since it's so convenient and well-documented.

I initially set up my site with support for DailyCred, which I only heard about because it was one of the template options for creating a new Luminus project. It seemed pretty easy to set up, and I got as far as redirecting users to DC and getting back the token, but at that point DC would complain that I was using an unknown client ID (even though it was a valid ID that worked correctly in their sandbox), and I'd be dead in the water. Finally I decided to fall back to a more conventional approach: today's project is to rip out all the DC stuff and replace it with Friend. Partly this was frustration with DC, and partly it was because I just got done watching this video, and wanted to take Friend for a spin.

Wednesday, January 11, 2012

Ah, a secret gateway into ClojureScript

I've been very interested in ClojureScript since it was first announced, but somehow I've never quite made it over that first hill. I think that may be about to change though:

ClojureScript One is a helpful resource for getting started with ClojureScript. It is not a library or a framework. It is an example with lots of documentation. We hope that by looking through this example and reading the documentation we can remove the barriers that are stopping you from experiencing how much fun ClojureScript development can be. Once you have this experience, we think you will be hooked.
You can find ClojureScript One on the web at
 I've downloaded the git repo and got the "Getting Started" stuff up and running in no time. Now if you'll excuse me, I have a REPL or two to play with...

Tuesday, January 10, 2012

The perfect language

I was browsing through Planet Clojure the other day and saw a post about "The Book the World Needs." Not to give away the plot, but the missing book is an introduction to functional programming for non-FP programmers.

I'm not the guy to write that book, but reading that post reminded me of some of my early programming experiences, and helped me understand what it is that I find so appealing about Clojure.

Sunday, November 27, 2011

What I've learned from Salty

I spent the weekend hacking at my Salty library for Clojure. Salty is a thin wrapper around the Selenium WebDriver framework, and it allows you to programmatically control a web browser like Firefox, as I've mentioned before. It turns out there is already a Clojure lib for WebDriver---clj-webdriver---that is full-featured, easy to use, and very mature. For that reason, I'm probably not going to invest too much more effort in Salty. But that's fine: I mostly wanted to try this as a learning exercise, and clj-webdriver makes it easier for me to check my homework. Here's a few notes on what I think I got right and what I think I got wrong.

Sunday, November 20, 2011

Re-formatting variable names

(Series: From PHP to Clojure)

Here's a simple problem: as part of my Salty lib, I want a function that will take camel-case variable names, as used by Java, and convert them to the dash format that's idiomatic in Clojure. In other words, I want a function that will take the string "someVariableName" (camel case)and return "some-variable-name" (with dashes).