[Haskell-cafe] monad subexpressions
cdsmith at twu.net
Thu Aug 2 15:39:36 EDT 2007
I've heard Simon (Peyton-Jones) twice now mention the desire to be able
to embed a monadic subexpression into a monad. That would be
http://article.gmane.org/gmane.comp.lang.haskell.prime/2267 and in the
recent OSCON video. Is someone working on implementing this?
If no, I'll take a crack at it.
If yes, I'd be slower than someone else, since I'm new to GHC.
This seems like something a tad easier than type system extensions and
the like since it's just desugaring... but a little harder than my
"remove the GHCi banner" patch! In other words, a perfect step for me.
Also, I got so frustrated that I ended up abandoning some code recently
because STM is, in the end, so darn hard to use as a result of this
issue. I'd love to see this solved, and I'm quite eager to do it.
Proposals for syntax I've seen include:
$( expr ) -- conflicts with template haskell
( <- expr ) -- makes sense, and I think it's unambiguous
``expr`` -- back-ticks make sense for UNIX shell scripters
(| expr |) -- I don't think anything uses this yet
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