24 Oct
2012
24 Oct
'12
6:08 a.m.
Is there a convenient way of handling a data structure with lots of fields of different types that may or may not be filled in? Something equivalent to data D = D {a::Maybe A, b::Maybe B, c::Maybe C, …} but with better space efficiency and a more convenient empty object. An easy alternative is data E = Ea A | Eb B | Ec C | … type R = [E] which has a straightforward empty object, but one then must define getA e = listToMaybe [a | Ea a <- e] for each field, which is tedious (and O(n)). Obviously Templates would help, but is there an alternative I’ve missed? -- Jón Fairbairn Jon.Fairbairn@cl.cam.ac.uk