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Expensive Egg-Timers

If you use a CLI you might have done something along the line.

sleep 1m 30s; do-the-next-thing

I have a script called OK that will display a short text in a hopeful green and morse code O-K via the PC speaker. By doing so I turn my computer into an expensive egg-timer.

As of late I found myself waiting for longer periods of time and was missing a count-down so I could estimate how much more time I can waste playing computer games. The result is a program called count-down.

Since I wanted to mimic the behaviour of sleep as closely as possible I had a peek into its source-code. That made me realise how lucky I am to be allowed to use Perl 6. If I strip all the extra bits a count-down needs I’m at 33 lines of code compared to 154 lines of GNU sleep. The boilerplate I have is mostly for readability. Like defining a subset called Seconds and a Rexex called number.

Errors in the arguments to the script will be cought by the where clause in MAINs signature. Since there are no further multi candidates for MAIN that might interfere, the usage message will be displayed automatically if arguments are not recognized. Pretty much all lines in the C implementation deal with argument handling and the fact that they can’t trust their arguments until the last bit of handling is done. With a proper signature a Perl 6 Routine can fully trust its arguments and no further error handling is needed. Compared to the C version (that does a lot less) the code can be read linear from top to bottom and is much more expressive. After changing a few identifiers I didn’t feel the need for comments anymore. Even some unclear code like the splitting on numbers and keeping the values, becomes clear in the next lines where I sum up a list of seconds.

Now I can comfortably count down the rest of a year that was made much better by a made better Perl 6. I wish you all a happy 2018.

Categories: Perl6
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