k.schupke at imperial.ac.uk
Wed Dec 29 13:17:30 EST 2004
Except for GHC, where a variable staring with an '_' will not report a
if it is unused in the body of a funtion:
let _ = x in y -- no warning
let result = x in y -- waring about result being unused
let _result = x in y -- no warning, but variable can still be used.
Duncan Coutts wrote:
>In message <20041229115341.A431 at botik.ru> "Serge D. Mechveliani"
><mechvel at botik.ru> writes:
>>Dear Haskellers, dear GHC team,
>>Is a variable `_x' equivalent to `_'
>No, '_x' is a perfectly ordinary variable. The only special "dummy variable" (a
>pattern that matches anything but does not bind a varialbe) is '_'.
>>Does really Haskell mean this? It this reasonable?
>>How to set self-commenting dummy variables?
>You can use them as dummy variables by never using them in an expression
>context, only in pattern/binding context. As you noted they should be unique
>withing each scope.
>Glasgow-haskell-users mailing list
>Glasgow-haskell-users at haskell.org
More information about the Glasgow-haskell-users