Consider the following simple Haskell program.
---8<---
import System
data Foo = Bar
| Baz
deriving (Eq,Ord)
main :: IO ()
main = do { argv <- getArgs
; case argv of
["forty-two"] -> print "HHGTTG"
_otherwise -> print "oh well"
}
---8<---
With this morning's ghc-4.03 and the -Wall option, I get the
following:
---8<---
sphere$ /homes/kw217/Scratch/Builds/i386-unknown-linux/fptools-4.xx-cvs/
ghc/driver/ghc-4.03 Test.hs -Wall
Test.hs:11: Warning: Defined but not used: _otherwise
Note: renameSourceCode found warnings
Test.hs:3: Warning: Defined but
not used: cmp_eq{-ryO-}
<compiler-generated-code>:
Warning: definition but no
type signature for
`con2tag_Foozh{-rxq-}'
ghc-4.03: module version unchanged at 2
sphere$
---8<---
Notice three things here.
1. Despite the following comment in the CVS log for 1999/01/14 17:59:10
sof:
* _ as lower-case letter, "_" is a reserved id. Prefixing unused
variable names in patterns with '_' causes the renamer not to
report such names as being unused.
we are getting a warning for `_otherwise'.
2. The formatting of the next two warnings leaves something to be
desired.
3. The warnings for cmp_eq and Foo# relate to internal GHC-generated
code, rather than anything the programmer has done wrong. (except
perhaps that the Eq and Ord dictionaries are not used; but then the
error message is rather unclear).
--KW 8-)
--
: Keith Wansbrough, MSc, BSc(Hons) (Auckland) ------------------------:
: PhD Student, Computer Laboratory, University of Cambridge, England. :
: (and recently of the University of Glasgow, Scotland. [><] ) :
: Native of Antipodean Auckland, New Zealand: 174d47' E, 36d55' S. :
: http://www.cl.cam.ac.uk/users/kw217/ mailto:[EMAIL PROTECTED] :
:---------------------------------------------------------------------:
