On Sep 30, 2014 7:12 AM, "Konrad Hinsen" <<a href="mailto:konrad.hinsen@fastmail.net">konrad.hinsen@fastmail.net</a>> wrote: > > Sam Tobin-Hochstadt writes: > > > Ah, if you want to create truly cyclic structure with no base case > > like this, then you'll have to do more work. Either you'll need to > > expand the type of the `x` field in `foo` to allow an initial value, > > or you'll need to create a dummy `foo` with that extended type, and > > then copy the cyclic data once you've created it to a new version > > In my specific application, I ended up replacing the cyclic data > structure, which was a singleton, by a function that simulates it. > But for another project, which involves graphs, I'll stick to > untyped Racket for now. Robby reminds me that we wrote a paper about another trick that might be useful here: <a href="http://www.ece.northwestern.edu/~robby/pubs/papers/stop2009-tf.pdf">http://www.ece.northwestern.edu/~robby/pubs/papers/stop2009-tf.pdf</a> Sam