On Feb 2, 2009, at 9:45 PM, Matthew J. Williams wrote:
Dear All How would one mimic, in Haskell, a C++ circular linked list i.e., where the last element precedes (points to) the first?
You are getting deep answers to what is perhaps a simple question. You haven't said exactly what you want to do with a circular linked list, and people are perhaps fearing the trickiest applications. Have you tried the Prelude function cycle?
cycle :: [a] -> [a] cycle ties a finite list into a circular one, or equivalently, the infinite repetition of the original list. It is the identity on infinite lists.
For instance, in ghci one gets
Prelude> [1..3] [1,2,3] Prelude> take 10 $ cycle [1..3] [1,2,3,1,2,3,1,2,3,1]
cycle doesn't actually construct in memory a cyclic data structure, as one might in C. It's more like those repeat bars in sheet music.