Add OEIS interface

[byorgey]

Using the oeis package. Provide some OEIS primitives that allow interaction with the OEIS database.

[bookshelfdave]

can you provide examples of what this could look like?

[byorgey]

Sure! The oeis package provides a way to retrieve all the info related to a sequence, but I am thinking of keeping things simple. Maybe we could have two primitives: one to extend a sequence, and the other to yield the URL of a sequence. So, in more detail:

• Add two new primitives, called something like lookupSequence and extendSequence.
  • Add them in Disco.Syntax.Prims, in both the Prim data type and the primTable. Probably make them non-exposed (i.e. set the boolean in the primTable to False).
  • Add them to the inferPrim function in Disco.Typecheck. I'm imagining type [N] -> String for lookupSequence and [N] -> [N] for extendSequence.
  • Add corresponding constants to the Op data type in Disco.AST.Core, and update the compilePrim function in Disco.Compile to trivially turn the new prims into the new Op constants.
  • Update the whnfOp function in Disco.Interpret.Core to handle the new constants. This is where you would actually write code to call the Haskell oeis package and convert back and forth to Disco runtime values.
• Add a new library module oeis.disco in lib/, and have it simply re-export the prims (you can see how this is done for num.disco as an example).
• Add some test cases to the test suite to exercise it.

[byorgey]

As a further example of what this might look like when it's working:

Disco> import oeis
Disco> :type extendSequence
extendSequence : List ℕ → List ℕ
Disco> extendSequence [0,1,1,2,3,5]
[0, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, 144, 233, 377, 610, 987, 1597, 2584, 4181, 6765, 10946, 17711, 28657, 46368, 75025, 121393, 196418, 317811, 514229, 832040, 1346269, 2178309, 3524578, 5702887, 9227465, 14930352, 24157817, 39088169, 63245986, 102334155]
Disco> :type lookupSequence
lookupSequence : List ℕ → List Char
Disco> lookupSequence [0,1,1,2,3,5]
"http://oeis.org/A000045"

I'm also open to other suggestions!