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Re: eval not working the way I expected?

by Errto (Vicar)
on Jan 09, 2008 at 19:08 UTC ( #661459=note: print w/replies, xml ) Need Help??

in reply to eval not working the way I expected?

One other thing - if the code inside the eval does produce a fatal error (and divide by zero is the only one I can think of unless the values are actually objects of a class that overrides arithmetic) you'll still get a warning printed for Use of uninitialized value in sprintf. The reason is that if the eval fails, it will return an undefined value. sprintf will coerce this to the number zero, but it will issue a warning in doing so. To avoid that, you can either disable warnings on the relevant block by saying no warnings; or you can do the conversion explicitly by saying something like eval { ... } || 0

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[ambrus]: overhead slide plus blackboard is inconvenient because the lighting conditions are different and they require separate areas you can't quickly repartition, and typing on keyboard is faster and more convenient than writing on a blackboard
[Corion]: (b) would be cool. I've thought about this doing Pod editing, and even simply regenerating/live updating the browser makes things much more interactive
[ambrus]: modern computers have way enough processing power to allow this, at least for geeks who are willing to spend a few weeks to learn a tricky new user interface like vim
[Corion]: ambrus: Well, for mathematical notation, I find blackboard much more convenient than a computer. But when inserting text or moving text around, the computer wins obviously
[ambrus]: But either of these is a big problem in practice, so I'd need to spend like thirty years of my life to solve (a) and five more years to solve (b)
[ambrus]: Corion: yes, CURRENTLY the blackboard is more convenient
[ambrus]: and it's not like I want to ban blackboards anyway
[ambrus]: you already have blackboards and a canvas for projector or overhead transparencies (or positive film slide projector, not used for maths) canvas in the same lecture halls today, and switch in a few minutes between presentations,
[ambrus]: they're only difficult to use together.
[ambrus]: overhead transparencies are a nice convenience by the way that mix the two slides, because you can write them in advance and edit them during the presentation easily. but they're not very much in fasion these days.

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