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Re: Why does perl math suck?

by tilly (Archbishop)
on Jan 29, 2011 at 15:39 UTC ( #885026=note: print w/replies, xml ) Need Help??


in reply to Why does perl math suck?

perl -le 'print 5056.45 + 10112.92 eq 15169.37 ? "as expected" : "perl math sucks!"'
works as expected. The reason is that Perl uses more digits in floating point calculations than it stringifies, so stringification rounds off to the expected number. (I didn't invent this trick.)

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[Corion]: Yesterday I encountered an interesting data structure problem. I have a remote program that emits events, and my client listens for these events with one-shot callbacks, that is, I register the callback and if the event gets generated that callback ...
[Lady_Aleena]: robby_dobby, every day. Chaos is my life with few controls.
[Corion]: ... gets called once. The data structure for that is just a hash of arrays, mapping the event type to a queue of registered one-shots, and the first one-shot from the queue gets removed and called.
[Corion]: But now I want to register a one-shot for two events, of which only one will arrive, so my data structure doesn't work anymore...
[Lady_Aleena]: Corion, ouchy.
[Corion]: (maybe I should write this up as a SoPW) - currently, the "most efficient" data structure I come up with is a single array which I scan for the first fitting one-shot. Not efficient but I don't expect more than five outstanding one-shots anyway
[choroba]: can't you create a meta-key corresponding to the disjunction of the events?
[robby_dobby]: Corion: Heh. This whole thing smells of Strategy Pattern or MVC pattern.
[Corion]: And performance linear to the number of registered one-shots doesn't feel that bad. Maybe I should collect statistics on how many callbacks are outstanding ;)
[Corion]: choroba: Yes, but the longer I thought about efficient hashes mapping the event type back to their callbacks, and how to keep them in sync, the more I thought that all that optimization might just not be worth it, even if it's horribly inelegant

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