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:
unlines . lines . unlines == {assoc (.)}
unlines . (lines . unlines) == {equation 1}
unlines . id == {id is unit of (.)}
unlines
I.e. in general, when f is g's left inverse:
f . g == id
Then the following equation holds automatically:
g . f . g == g
Regards,
/Koen.
--
Koen Claessen
http://www.cs.chalmers.se/~koen
Chalmers University, Gothenburg, Sweden.
_______________________________________________
Haskell mailing list
[EMAIL PROTECTED]
http://www.haskell.org/mailman/listinfo/haskell
