On Fri, 8 Oct 2010 01:13:20 +0300, Lauri Alanko <l...@iki.fi> wrote: > On Thu, Oct 07, 2010 at 02:45:58PM -0700, Nicolas Pouillard wrote: > > On Thu, 07 Oct 2010 18:03:48 +0100, Peter Wortmann <sc...@leeds.ac.uk> > > wrote: > > > Might be off-topic here, but I have wondered for a while why Haskell > > > doesn't support something like follows: > > > > > > do case (<- m) of ... > > > > > > With the more general rule being: > > > > > > do ... e (<- m) g > > > => > > > ... m >>= \tmp -> e tmp g > > Your "general" rule doesn't subsume your case example, since a case > expression is not an application. I think you mean something like > > do C[(<- m)] > => > m >>= \tmp -> C[tmp] > > where C is an arbitrary expression context. It could further be > generalized to allow several (<- ...) subterms in an expression, with > implied left-to right sequencing. Frankly, that seems like a very > attractive way to make the do-notation into a more practical > imperative sub-language.
This is clearer. However this does not seems very robust against manual refactoring of the "do" notation. Imagine find this code: do s1 C[(<- s2)] And I don't see the (<- s2) in C, and so I refactor it as: s1 >> C[(<- s2)] And so the s2 get affected somewhere else. -- Nicolas Pouillard http://nicolaspouillard.fr _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
