
Gamifying mathematics (an interactive tutorial for sequent calculus) - ezyang
http://logitext.ezyang.scripts.mit.edu/logitext.fcgi/tutorial?
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haliax
The linked book by Pierce is pretty fantastic as well.
<http://www.cis.upenn.edu/~bcpierce/sf/>

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rprospero
I've been working on a similar project for high school algebra. Mine isn't as
far along, so it's been nice to see some validation on my ideas, as well as
get some thoughts on how I would improve.

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fusiongyro
How do you make contraction happen? I don't see a button for it.

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ezyang
We do contraction on implication-left automatically, and only have it as an
option for forall-left and exists-right, since it's not a useful notion for
the other operators.

