On Tue, Dec 01, 2009 at 12:40:33PM +0000, Duncan Coutts wrote: > On Mon, 2009-11-30 at 23:30 +0000, Ian Lynagh wrote: > > On Mon, Nov 30, 2009 at 11:05:21PM +0000, Duncan Coutts wrote: > > > On Mon, 2009-11-30 at 17:26 +0000, Ian Lynagh wrote: > > > > > > > f2 x = x + case () of > > > > () -> x > > > > where x = 5 > > > > > > 10, same reason. > > > > So if you look at f2 from the perspective of someone new to the > > language, given they understand the scoping of f1 and f3, would they > > expect that where binding to scope over the entire RHS rather than just > > the case expression? Maybe it's just me, but I don't think that would > > match my intuition. > > They would know that it has to be one or the other. The new person would > reason that the language designers either picked > or >= for column > offset. Which one they picked is something a new person would have to > look up, or just try, or avoid. > > >From a casual perspective there's nothing subtle about this case, it > does just look like a question of an arbitrary choice between >= vs >. > Programmers don't (and do not have to) realise that in reality parsing > this relies on the error rule.
Let me try asking it another way: If in H98 the above was an error, and we were discussing what to change it to, how would you rank the options? My answer would be: 1: Keep it as an error; no real need/benefit to make it a special case 2: The bindings should scope over the case expression only, as the where clause looks like it "belongs" with the case expression 3: Scope over the whole function Thanks Ian _______________________________________________ Cvs-ghc mailing list [email protected] http://www.haskell.org/mailman/listinfo/cvs-ghc
