On Wed, 22 Jul 1998, Ralf Hinze wrote:
> What about `&' for catenation?
I would be more inclined to use <<. The reason is typing efficiency.
'&' is awkward to be typing frequently immediately after '"'.
You are acutally using (.) below. Is there a way to do that (via
Fran like lifting?)?
> > instance Stringable ShowS where
> > toStrings = id
>
> This instance declaration is necessary to make `&' useable. Note that
> this is not (Standard) Haskell but works only with Hugs 1.3c (and
> probably with GHC's next release).
Why does this instance declaration require 1.3c? Also, are there
substantive differences between Hugs 1.3c and GHC 3.3? Are people
prototyping w/ 1.3c and then planning to build with the next GHC?
> > (&) :: (Stringable a, Stringable b) => a -> b -> ShowS
> > a & b = toStrings a . toStrings b
>
> Note that `&' yields `ShowS' and not `String'.
>
> > val = "the sum of 2 and 2 is " & (2 + 2 :: Int) & " whenever."
> Furthermore note that `val' has type `ShowS'. If quadratic time
> behaviour is not a problem (does not occur?) you can safely omit the
> `Stringable ShowS' instance and change `&' to `toString a ++ toString b'.
I am not understanding this last bit. Can you explain further?
> `render' is quite flexible:
>
> ? render val
> the sum of 2 and 2 is 4 whenever.
> ? render (toString "aaa")
> aaa
> ? render "aaa"
> aaa
> ? render (toStrings "aaa")
> aaa
Very cool. Thank you.
> ===============================================================================
>
> > Is there any way to convince Haskell to just resolve these numbers to
> > SOMETHING by default? Then I can just declare that type an instance of
> > Stringable.
>
> Unfortunately not. I did not succeed in persuading SPJ ;-). See
>
> http://www.cs.chalmers.se/~rjmh/Haskell/Messages/Display.cgi?id=445
It sounds like he just wants more votes for this change. I just added
mine (for whatever thats worth :-))
-Alex-
___________________________________________________________________
S. Alexander Jacobson i2x Media
1-212-697-0184 voice 1-212-697-1427 fax
