Except for GHC, where a variable staring with an '_' will not report a warning 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. Keean. Duncan Coutts wrote:

In message <20041229115341.A431@botik.ru> "Serge D. Mechveliani" 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 '_'.

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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.

Duncan _______________________________________________ Glasgow-haskell-users mailing list Glasgow-haskell-users@haskell.org http://www.haskell.org/mailman/listinfo/glasgow-haskell-users