Re: Re : [Haskell-cafe] Indentation woes

On Thu, Jul 26, 2007 at 05:34:32PM -0400, anon wrote:

2007/7/26, Stefan O'Rear :

...

As for "why", it's just a matter of Haskell Committee taste. Nothing too deep, just an arbitrary set of rules. That's not much of an explanation, is it? I imagine someone must have given the matter some thought before describing the layout rule in great details in the language report. Perhaps there was a perfectly good reason to preclude this kind of code, but I'm afraid I do need a reason if I am to understand why.

Part of the reason is that the layout rule is supposed to be somewhat independent of the rest of the grammar. It's described as a simple preprocessing state that adds block delimiters { ; } just recongizing a few keywords that open blocks, and otherwise looking at the indentation of the first non-whitespace character on lines. You can allow the syntaxes where something is no less indented than it's containing block by allowing some optional semicolons in the grammar. GHC keeps it's parser in compiler/parser/Parser.y.pp It's a Happy grammar file, it shouldn't be hard to make your change and see how you like it. I think the "gdrh" nonterminal is the one you want to change, add another production that allows ';' '|' quals '=' exp Have fun Brandon Moore