[Haskell-cafe] extra semi-colons

[Johannes Waldmann]

Dear Cafe,


why does ghc accept the extra semi-colon in

   case () of { () -> (); }

or even

   case ()  of  { ;;; () -> () ;;; }


Yes I understand that semicolons like this
are introduce by the layout rule

   L (<n> : ts) (m : ms) = ;  :  (L ts (m : ms)) if m = n

https://www.haskell.org/onlinereport/haskell2010/haskellch10.html#x17-17800010.3

and it's convenient to ignore extra ones.


But it's not in the grammar?

   alts 	→ 	alt1 ; … ; altn 	    (n ≥ 1)

https://www.haskell.org/onlinereport/haskell2010/haskellch3.html#x8-460003.13


- J.