Language.Haskell.Parser and layout rules

John Meacham john at
Fri Feb 18 19:54:56 EST 2005

On Thu, Feb 17, 2005 at 02:17:42PM +0000, Malcolm Wallace wrote:
> Ross Paterson <ross at> writes:
> > The Report (section 9.3, especially notes 1 and 2) says "A nested context
> > must be further indented than the enclosing context", so this is illegal.
> > GHC and Hugs have innovated here, ...
> I see you are using "innovated" here in the Microsoft sense, meaning
> "undocumented and incompatible departure from standards".  :-)

I think of this as a very useful feature. it should be documented in the
extensions section. mainly, I find it very useful in two circumstances:

short circuit return:

main = do
        if bar then return baz else do

with declarations

main = do
        withCString x $ \x' -> do
        withCString y $ \y' -> do
        c_func x' y'


John Meacham - ⑆⑆john⑈ 

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