I had not!
I'm not seeing how such a solution would work. The nodes in a graph all
have to have the same type. If the phantom parameter distinguished two
nodes, they could not be used together.
But maybe you see something there that I don't?
On Thu, Feb 18, 2016 at 8:36 PM, Francesco Ariis
Suppose then you wanted to write a function that, given a person, returns the names of all their hamsters. To make sure the call makes sense, the function would have to first check that the input is in fact a person. Since persons and hamsters are both constructors of the same type, you can't let Haskell's robust, beautiful type-checking system distinguish
On Thu, Feb 18, 2016 at 06:50:26PM -0800, Jeffrey Brown wrote: them
for you; you've got to write something like "case n of Person _ -> True; _ -> False".
Is there some way around writing such manual checks?
Hello Jeffrey, have you considered using Phantom types [1]?
[1] https://wiki.haskell.org/Phantom_type#Simple_examples _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://mail.haskell.org/cgi-bin/mailman/listinfo/haskell-cafe
-- Jeffrey Benjamin Brown