Ralf Hinze wrote:
| Isn't this a consequence of parametricity?] `show []'
| should produce `[]' and `show ""' should produce `""'.
Hi Ralf, take a look at the following example:
data Bit = Low | High
instance Show Bit where
showsPrec _ Low = showChar '0'
showsPrec _ High = showChar '1'
showList bits
= showChar '<'
. foldr (.) id (map shows bits)
. showChar '>'
In Hugs:
Main> [Low, Low, High, Low]
<0010>
Main> []
ERROR: Cannot find "show" function for:
*** expression : []
*** of type : [a]
Main> [] :: String
""
Main> [] :: [Bit]
<>
I hope this convinces you.
Regards,
Koen.
--
Koen Claessen,
[EMAIL PROTECTED],
http://www.cs.chalmers.se/~koen,
Chalmers University of Technology.
