[Haskell-cafe] Questions on the Haskell 2010 report

[Silvio Frischknecht]

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I am trying to write a haskell compiler and i have stumbled upon 2
issues that i don't understand in the Haskell report 2010. Btw. these
issues are also present in the 98 report.

1)
first is this in section 5.1 Module Structure [1]. A module is defined
like this.

	module 	→ 	module modid [exports] where body
		| 	body
	body 	→ 	{ impdecls ; topdecls }
		| 	{ impdecls }
		| 	{ topdecls }

You can't see it in this mail because there is no font but
the curly braces { } are meant to match the tokens { } and are not
meant as repetition. However, as I understand it, the layout parser
would modify this code:

	module Foo where
	import Bar
	baz=baz

to this code (which doesn't match):

	module Foo where { import Bar ; baz=baz }

and not to this code (which would be required to match):

	module Foo where { { import Bar } ; { baz=baz } }

So as i see the definition should state this instead:

	module 	→ 	module modid [exports] where body
		| 	body
	body 	→ 	{ impdecls ; topdecls }
		| 	impdecls
		| 	topdecls

2)
In the same section what is it supposed to mean if "module" consists
of only a "body" and not "module modid [exports] where body".

3)
In section 10.3 Layout [2] it is written.

If a let, where, do, or of keyword is not followed by the lexeme {,
the token {n} is inserted after the keyword, where n is the
indentation of the next lexeme if there is one, or 0 if the end of
file has been reached.

Together with this rule

	L [] (m : ms) = }  :  L [] ms         if m≠0 (Note 6)

This results in an error if the program ends in a "where", ...
Wouldn't it make more sense to put a {1} in case of EOF or just insert
the tokens '{' and '}'. On the other hand if you really won't accept
that why not simply say that it is an error.

btw. GHC doesn't give an error.

[1]
http://www.haskell.org/onlinereport/haskell2010/haskellch5.html#x11-990005.1
[2]
http://www.haskell.org/onlinereport/haskell2010/haskellch10.html#x17-17800010.3
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