If its monadic code then use Control.Monad.when.
If its pure code then omitting the 'else' clause makes no sense
what-so-ever; to omit the else you must know the boolean is always true so
why have the if? See the "Common Misunderstandings" [1] page I put together
in response to seeing one too many people trip over exactly this issue.
Thomas
[1] http://haskell.org/haskellwiki/Common_Misunderstandings
On Wed, Oct 21, 2009 at 5:43 PM, michael rice
It looks like both the THEN and the ELSE in an IF expression must each have an expression. What's a graceful way to do nothing in either or both slots, kind of like the Fortran CONTINUE statement.
--mr
================
[michael@localhost ~]$ ghci GHCi, version 6.10.3: http://www.haskell.org/ghc/ :? for help Loading package ghc-prim ... linking ... done. Loading package integer ... linking ... done. Loading package base ... linking ... done. Prelude> if (1==1) then else
<interactive>:1:15: parse error on input `else' Prelude> if (1==1) then True else
<interactive>:1:24: parse error (possibly incorrect indentation) Prelude> if (1==1) then True else False True Prelude>
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