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5 votes
0 answers
1k views

What's the general idea (intuition) behind Andrej's topos where reals are countable? [closed]

I am very surprised that Andrej Bauer claimed to have found a topos where reals are countable. He said it'll take a month to write down the proof, and I think that's very understandable. However, I'm ...
ice1000's user avatar
  • 6,316
14 votes
4 answers
321 views

Algorithms obtained through constructive formalization

Formal proofs in proof systems that avoid the law of the excluded middle and certain other principles can be automatically converted into algorithms. What useful new algorithms have been produced by ...
Will Sawin's user avatar
27 votes
8 answers
961 views

Where can I find lists of theorems that have been verified?

I recall many years ago seeing a very large and well-interlinked (by computer) list of verified results starting from base assumptions and leading to all sorts of things that naive me did not expect ...
18 votes
2 answers
401 views

How can I prove facts about floating point calculations?

In computing, there is a standard called IEEE 754. Unlike in mathematics, computers have to fit numbers into a finite amount of space; to do this, they use a format a bit like scientific notation, ...
wizzwizz4's user avatar
  • 495