the dreaded offside rule

[Lennart Augustsson]

If you can parse "do x == y == z" or "case 0 of x -> x == x == True"
you're probably ok.  I can't tell from your example if this works
or not.

	-- Lennart

Doaitse Swierstra wrote:
> 
> On 2006 mrt 09, at 1:54, Lennart Augustsson wrote:
>> I agree with it being complicated.  I don't know of any compiler
>> that implements it correctly.  Do you say your combinators do?
> 
> At least we think so. The way to use it is e.g.:
> 
> pExprPrefix     =    sem_Expr_Let  <$ pKey "let" <*> pDecls  <* pKey "in"
> 
> pDecls          =    foldr sem_Decls_Cons sem_Decls_Nil
>                                          <$>  pBlock pOCurly pSemi 
> pCCurly pDecl
> 
> pDecl           =    sem_Decl_Val        <$>  pPatExprBase  <*   pKey 
> "="   <*> pExpr
>                 <|>  sem_Decl_TySig      <$>  pVar          <*   pKey 
> "::"  <*> pTyExpr
> 
> in which the pBlock takes care of the offside rule, in cooperation with 
> the scanner.
> 
>>
>> That said, I don't think it can be replaced easily without breaking
>> existing code, so I'm unwilling to change unless someone can show
>> an alternative that handles 99.9% of the existing code.
> 
> There are solutions to this kind of transitions. Compilers could admit 
> the old rule, and emit a warning when e.g. the 
> --this-is-supposed-to-be-strictly-haskell-prime flag is passed. One 
> might also equip a compiler to transform one's program into the new 
> standard.
> 
> 
>  Doaitse
>