On 2008 May 4, at 23:40, Ross Boylan wrote:
ERROR "grammar.hsl":21 - Type error in explicitly typed binding
*** Term : envEnd
*** Type : String -> GenParser Char a [Char]
*** Does not match : String -> Parser ()
Hugs is prone to error messages that obscure the problem. The trick
here is to realize that the type "Parser ()" is the same as "GenParser
Char a ()"; this then tells you that you have used a function that
returns a [Char] (aka String) where a type () (Haskell's version of
(void)) is expected.
envEnd :: String -> Parser ()
envEnd name = do{ reserved "\\end"
; braces (string name)
}
Line 21 is "; braces (string name)"; it is producing a String, when
you need a (). One fix is to add one more line:
> envEnd :: String -> Parser ()
> envEnd name = do reserved "\\end"
> braces (string name)
> return ()
Another possible fix is to change the type of "envEnd" to "String ->
Parser String"; this may depend on how it's used.
--
brandon s. allbery [solaris,freebsd,perl,pugs,haskell] [EMAIL PROTECTED]
system administrator [openafs,heimdal,too many hats] [EMAIL PROTECTED]
electrical and computer engineering, carnegie mellon university KF8NH
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