lines/unlines and "inverse"

[Lars Henrik Mathiesen]

> From: Koen Claessen <koen@cs.chalmers.se>
> Date: Mon, 22 Jul 2002 11:25:16 +0200 (MET DST)

> Lars Henrik Mathiesen wrote:
>
>  | lines . unlines = id
>  | unlines . lines . unlines == unlines
>  | words . unwords . words = words
>
> Don't be fooled by the information content of the second
> equation -- the first equation directly implies it:

But as Wolfgang noted, the first equation does not actually hold. I
have to admit to getting a brain malfunction just before sending my
post and mis-correcting my original, which was

      lines . unlines . lines = lines

So, while your implication is true, the antecedent isn't, and thus the
second equation does have some information content...

Lars Mathiesen (U of Copenhagen CS Dep) <thorinn@diku.dk> (Humour NOT marked)