At first, thanks to all of you about this nice insight into FP used
programmers. It was really a suprise to me to see that that what Sven
wrote seems to be easily understood. I would really like to see such
code-snippets to found on a central site what about www.haskell.org ?
I reread my book and there the chapte about functional composition or
the like and I found the stuff I didn't understand. So maybe it's time
to re-read the book again ;-)
>
> longerThan fn lenlim
> = readFile fn >>= procFile
>
> procFile
> = putStr .
> unlines .
> (map (\ (n,l) -> show n ++ ") " ++ l)) .
> (zip [1..]) .
> (filter ( (>lenlim) . length ) ) .
> lines
This seems to be not workable and I tried it by myself.
this is my Result:
lt1 fn lenlim = readFile fn >>= procFile lenlim
procFile lenlim = putStr .
unlines .
(map(\(n,l) -> show n ++ ")" ++ l)) .
(filter ((> lenlim) . length . snd )) .
(zip [1..]) .
lines
this seems to to the thing I would like it to do. I now have to check if
the given fn is valid and raise an error if not so I do think I'll make
it;-)
Another thing is that I prefer for
(.|) = flip (.)
(>.>) = flip(.)
I think that's a matter of tast an both are familar. The .| reminds me
of a pipe-symbol and > shows me the flow. So ok Both are quite ok
althought I'm quite aware taht f . g maybe well known in mathematics.
But it's quite amazing how many possibilities you have to express that.
This makes it very expressive but IMO terrible difficult to understand.
I hope I get used to use the "right" mental model for FP someday. And I
hope I then won't the obfuscatd code but the beauty of Functions.
Thanks to Keith to explain to me in detail what is meant by the code
excepts. I rethink about it, read it again and now it's getting clearer
and clearer each time. Another 1000 examples and I may be familia with
it ;-)
So please allow me another question. Is that a way such functions are
build? How it that reused? Does it make sense to write some extra
functions for intermediate steps or should I try to learn that kind of
programming.
I have some problems with it because a lot of work is just done in one
Method. My knowledge comes from OO-programming and there it wouldn't be
good style to do so much in one function.
Regards
Friedrich
