On 18 March 2012 19:29, ARJANEN Loïc Jean David
Good point, but rather than specifying in the standard that the new string type should be the Text datatype, maybe the new definition should be that String is a newtype with suitable operations defined on it, and perhaps a typeclass to convert to and from this newtype. The reason of my remark is although most implementations compile to native code, an implementation compiling to, for example, JavaScript might wish to use JavaScript's string type rather than forcing its users to have a native library installed.
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. This is unfortunate since GHC's built-in mechanism actually uses unpackCString[Utf8]# which constructs the inefficient String representation from a compact memory representation. I think it would be best if the new fromString/fromText class allowed an efficient mechanism like that. unpackCString# has type Addr# -> [Char] which is obviously GHC-specific. -- Push the envelope. Watch it bend.