[Regex-tut] Cleaning it up

[wtd]

Quick recap

Last time, we ended up with the following regular expression that does a decent job of matching a greeting or parting message for world.

code:

/^\s*([hH]ello|[tT]oodles),?\s+world\s*$/

It looks like gobbledy-gook

Go ahead, say it. It's not pretty, is it?

Part of the appeal of regexes is that they allow programmers to express powerful patterns without having to write a lot of code. If you know what you're doing, they're reasonably easy to read. Still, it's nice that Ruby (and Perl) gives us a way to clean them up.

Spit it out already man!

The "x" modifier for a regular expression makes whitespace in the regular expression meaningless, so we can use it to separate things in the expression.

code:

/^ \s* ( [hH]ello | [tT]oodles ) ,? \s+ world \s* $/x

It gets better

Since whitespace is nothing to these regular expression, we could break this up and comment it.

code:

/    ^         # beginning of the string    \s*       # zero or more whitespace characters    (         # start group       [hH]   #either h or H       ello    |       [tT]   # either t or T       oodles    )         # end group    ,?        # one or zero commas    \s+       # one or more whitespaces    world    \s*       # zero or more whitespace characters    $         # end of string /