http://qs321.pair.com?node_id=1224722


in reply to Implementing a 2-mode "Audiobutton" on the Raspberry Pi

 if($lastswitch == -1) {

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Magic numbers are bad. Here's why.


holli

You can lead your users to water, but alas, you cannot drown them.

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Re^2: Implementing a 2-mode "Audiobutton" on the Raspberry Pi
by cavac (Parson) on Oct 29, 2018 at 15:37 UTC

    In many cases, yes, you are right. But in this case, at least in my opinion, the usage is quite clear. The switch could either be on (1) or off(0) or we don't know yet (-1 = number that could never happen otherwise). And i even bothered to document it:

    my $lastswitch = -1;

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    The whole $lastswitch thing could just be set to 0 on startup in theory (guessing the button isn't pressed on startup). Or i could just replicate the Device::BCM2835::gpio_lev($testpinnumber) call at the beginning.

    I just kept this one-off script for my one-off device to my usual style guide of 15+ years of Perl coding. If i see that construct, i instantly know i'm dealing with an uninitialized boolean. Same goes for other "magic" numbers. 3600 is seconds per hour, 86400 is seconds per day and 365.25 is (average) days per year.

    Those kinds of magic numbers i wouldn't call "bad", it's more of a grey area.

    I can completely understand your point of view, and in most cases i'd support you all the way, but i hereby invoke my right of TIMTOWTDI 😉

    perl -e 'use MIME::Base64; print decode_base64("4pmsIE5ldmVyIGdvbm5hIGdpdmUgeW91IHVwCiAgTmV2ZXIgZ29ubmEgbGV0IHlvdSBkb3duLi4uIOKZqwo=");'
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      3600 is seconds per hour, 86400 is seconds per day

      Yesterday in the UK we had 90,000 seconds. In the hour from 1am to 2am we had 7200 seconds. Magic numbers will get you in the end.

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In Section Cool Uses for Perl