Day 8, What are regular expressions?

If you don’t know about regular expression matching, or regex, it’s basically a language to find the useful needles in haystacks of text and code. Think ‘find and replace’ turned to 11.

I do just enough regular expression matching to forget how it works. I always end up googling for a quick reference, not quit finding what I need. My text editor of choice, SubEthaEdit has a nicely-formatted pattern reference in the Help menu, though it lacks ‘How RegEx Works’ documentation.

Enter Day 8 of Teach Yourself Ruby in 21 days. Everything about regex is covered; groupings, greediness, repetition, alternators, everything. A while back, I was thinking of picking up one of the many books specifically covering Regex. Now, I’m sure this one chapter will serve me well as that reference.

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This post documents my journey through Sam’s Teach Yourself Ruby in 21 days. I’ll be joining Al Abut in his effort to learn Ruby and blog along the way.

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Day 7, playing catch-up.

I’m continually impressed with how concise the Ruby language is. As I mentioned in Day 4, Ruby frowns upon loops. I’m getting the impression Ruby also frowns upon taking up 2 or more lines to describe an action. Slagell’s examples of doing something a traditional way take up multiple lines, his here’s-a-better-way examples are single line. If we compare writing code to writing words and say each a chunk of code is a paragraph and each line of code is a sentence. Writing Ruby is more like dialog than narrative.

Note to self:
In Ruby, double quotes acknowledges backslash-escaped characters, i.e. "n" = new line. Single quotes will not, i.e. 'n' = n. Same is true for evaluating expressions within #{...}

Two Cool Things in Ruby:

1. Chained Assigment
   Want to give a number of variables the same value?
   DaveSpeaks = JoeSpeaks = KatSpeaks = FrankSpeaks = "English"
2. Multiple Assignment
   Want to quickly set the values of multiple variables at the same time?
   DaveSpeaks, JoeSpeaks, KatSpeaks = "English", "Dutch", "German"

The start of the day has quite a bit on binary numbers. I’m not sure when binary arithmetic will come in handy (a position I also expressed regarding Jr. High Algebra) but it’s nice to know it’s here when the need arises. The example Slagell offers at the chapter end feels like a band-aid for a poorly designed system. If any of you following along can provide a comment on when it’s beneficial to use binary arithmetric, I’d be extremely grateful.

As I finished up today’s exercises, Bic Runga’s ‘Listening for the Weather’ came through my iTunes. What an excellent way to wrap up Day 7.

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This post documents my journey through Sam’s Teach Yourself Ruby in 21 days. I’ll be joining Al Abut in his effort to learn Ruby and blog along the way.

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Day 6, How to deal with files and other data streams.

What’s a reliable way to get the last item in an array? ask for the -1 item, i.e. array[-1].
Finally, a logical reason to start arrays at 0 rather than 1 – so we can count backwards.

Looks like the “then” part of an “if…then” statement can come first. As in this example from the book, removing a leading zero from a decimal number.
avg[0,1] = '' if avg[0, 2] == "0."

This will take some getting accustomed to. I’m more familiar with it written this way:

if avg[0,2] == "0."
avg[0,1] == ''
end


To accommodate When Bad Things Happen, Ruby has a pretty cool construct:

begin
#...
rescue BadThing1Happened
#...
rescue BadThing2Happened
#...
end


Two cool things here; first – this seems like a simple way to write more readable code – error conditions or otherwise, second – the word “rescue”, makes you feel like a superhero for catching Bad Things. Incentive enough for writing better code.

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This post documents my journey through Sam’s Teach Yourself Ruby in 21 days. I’ll be joining Al Abut in his effort to learn Ruby and blog along the way.

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