Original-Via: uk.ac.ox.prg; Mon, 4 Nov 91 13:52:20 GMT
Kent Karlsson asks:
| Which semantics did you use?
The following seemed sensible to me (Your first choice in each case):
For p+k patterns: (as in the report):
case e0 of {p+k -> e; _ -> e'}
= if e0 >= k then let {p = e0-k} in e else e'
For c*p patterns:
case e0 of {c*p -> e; _ -> e'}
= if e0 >= 0 && e0 `rem` c == 0
then let {p = e0 `div` c} in e
else e'
I think these would agree with Tony Davie's original proposal in the special
case of c*x+k patterns?
| Any syntactic restrictions on c or k (e.g. k >= 0, c >= 1)?
I think I had k>0, c>1, but I guess your limits are just as good.
| Note, I'm not opposing anything here, I'm just asking!
|
| /kent k
And I'm not suggesting that Haskell has p+k and c*p patterns.
I implemented them so that I could play with the ideas involved.
I'm not particularly convinced either way whether they should
be adopted or not.
Mark
