Dan Weston wrote:
Brandon S. Allbery KF8NH wrote:
On Feb 8, 2008, at 11:14 , Stefan Monnier wrote:
You seem to write 12 as 1 :+ 2 instead of () :+ 1 :+ 2. But I think, the latter representation should probably be prefered. (...) How 'bout treating :+ as similar to `append' rather than similar to `cons'? Basically treat :+ as taking 2 numbers (rather than a number and a digit).
Dumb questions department: why not define e.g. D'0 .. D'9 as () :* 0 .. () :* 9? Programmers then get D'1 :* 2, but the library sees () :* 1 :* 2.
No, D'0 should be (), not () :* D0. If you allow () :* D0, then you introduce redundant types for the same number:
In the first case, D'0 :* D'3 == D'3, and D'0 :* D'0 has no instance. In your example, D'3 and D'0 :* D'3 are equivalent, but no longer unify.
Dan
On second thought, how would you write D'3 :* D0 ? I think maybe using the () makes it fundamentally difficult to restrict multiple types for the same number.