Le 20/03/2012 16:29, Tillmann Rendel a écrit :
Hi,
Thomas Schilling wrote:
I agree that the language standard should not prescribe the
implementation of a Text datatype. It should instead require an
abstract data type (which may just be a newtype wrapper for [Char] in
some implementations) and a (minimal) set of operations on it.
Regarding the type class for converting to and from that type, there
is a perhaps more complicated question: The current fromString method
uses String as the source type which causes unnecessary overhead.
Is this still a problem if String would be replaced by an
implementation-dependend newtype? Presumably, GHC would use a more
efficient representation behind the newtype, so the following would be
efficient in practice (or not?)
newtype String
= ...
class IsString a where
fromString :: String -> a
The standard could even prescribe that an instance for [Char] exists:
explode :: String -> [Char]
explode = ...
instance IsString [Char] where
fromString = explode
Tillmann
A recent message on Haskell-café made me think that if the standard
mandates that any instance exists, it should mandates that an instance
exists for CString and CWString (C's strings and wide strings) or, more
generally, that an instance exists for any foreign string type defined
in the FFIs implemented. That is to say, if you implement a FFI for .Net
and you expose .Net's string type, you should implement conversions
between that string type and Haskell's one.
Regards,
ARJANEN Loïc
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