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GaloisInc / cryptol

Cryptol: The Language of Cryptography
https://galoisinc.github.io/cryptol/master/RefMan.html
BSD 3-Clause "New" or "Revised" License
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Enigma example in "Programming Cryptol" needs to be updated #1745

Open smithdtyler opened 2 months ago

smithdtyler commented 2 months ago

In section 3.2, the call to elem in mkRotor is incorrect, as elem does not take a tuple. 

mkRotor : {n} (fin n) => (Permutation, String n) -> Rotor
mkRotor (perm, notchLocations) = [ (p, elem (p, notchLocations))
| p <- perm
]

Should be 

mkRotor (perm, notchLocations) = [ (p, elem p notchLocations)
                                | p <- perm
                                ]
sauclovian-g commented 2 months ago

It's more complicated than that since this elem is a private definition (see line 762 of Enigma.tex for the copy that's used here) so one should change not just this usage, but also that definition and also the real one elsewhere in the book that the comment about an exercise refers to. And there are other references scattered around the book, some of which use one signature and some the other, and they should probably all be updated as well.

Is there any reason that one would deliberately use a different type signature for the exercise version? Or is it all just Olde?

yav commented 1 week ago

I think in old Cryptol things used to take tuples as arguments more often, because a long time ago there was an idea that maybe Cryptol could kind of look like C. So, quite likely, this falls directly in the "olde" category.