Ruby, Day 2: Thoughts
I originally learned Ruby (and many other programming languages) the “hacker way”: that is, I did a 10 minute syntax tutorial, browsed other peoples’ code a bit, and then just started using the language, looking up missing pieces as I went. Although this is the most fun and productive way I’ve found to get started with a language, it can also lead to missing some of the finer points and subtleties.
For example, until the “Ruby, Day 2” chapter, I never had a full appreciation for Ruby code blocks and the yield keyword. For example, even though I frequently used “times” to do looping, I never thought deeply about how it worked:
It turns out that
times is just a function (slightly obscured because Ruby
doesn’t require parentheses for function calls) on the
Integer class that
takes a code block as an argument. It could be implemented as follows:
This style of coding allows for some powerful possibilities. For example, it is surprisingly easy to introduce a “do in a transaction” function:
Using this, I can now trivially wrap any number of statements in a transaction:
The equivalent in less expressive languages, such as Java, often involves vastly more code, implementing arbitrary interfaces, anonymous inner classes, and a lot of very hard-to-read code. For comparison, here is an example of how Java’s Spring Framework recommends wrapping JDBC code in transactions:
Ruby, Day 2: Problems
The Day 2 problems are only slightly tougher than Day 1. The most fun part was coming up with a way to keep the code as concise as possible.
Print the contents of an Array of 16 numbers, 4 numbers at a time, using just
each. Now, do the same with
Tree class initializer (original code
here) so it can
accept a nested structure of Hashes. Trickiest part here was that the
collect function can call the passed in block with either one argument
that’s an Array or two arguments that represent the (key, value) pair.
Write a simple grep that will print the lines and line numbers of a file having any occurrence of a phrase anywhere in that line.
Ruby vs. Java, Round 2
I couldn’t resist implementing the grep code in Java to see how it compares:
It’s 33 lines long. The Ruby solution was a one-liner.
Check out more Ruby goodness on Ruby, Day 3.