David Roundy wrote:
On Wed, Aug 08, 2007 at 02:20:39PM -0400, Paul Hudak wrote:
As long as the sugar has a pretty obvious desugaring (which I seem to
recall it did), I don't see how it's likely to make things worse. And
Some people are arguing that the desugaring isn't obvious.
Although I like the proposal to start with, I am beginning to be
convinced by those arguments.
For example:
> do foo x
can be simplified to
> foo x
under the new proposals
> do x <- bar y
> foo x
would shorten to
> do foo (<- bar y)
and now you really really want to remove the do, to get simply
> foo (<- bar y)
but that would be illegal. The new sugar is going to remove all kinds of
substitution and simplification lemmas that we have got used to.
There is also the fact that if :
foo x = bar x x
then you call foo monadically as in
do foo (<- baz)
You can no longer "replace foo with its definition", because if replace
that with
do bar (<- baz) (<- baz)
...that means something rather different :(
A third example is with nested dos:
do x <- bar y
baz
something $ do foo x
is not the same as
do baz
something $ do foo (<- bar y)
Jules
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