[Haskell-cafe] Re: First time haskell - parse error!

Maciej Piechotka uzytkownik2 at gmail.com
Wed Mar 10 10:01:33 EST 2010

> > Good names can help making comments less important.
> OTOH, comment can give you the best(?) of both worlds, both revealing
> the linear structure of the function, while still providing extra
> information: 
>     oddSquareSum :: Integer
>     oddSquareSum = sum                 -- add together
>                  . takeWhile (<10000)  -- until a value >10K is seen
>                  . filter odd          -- all the odd
>                  . map (^2)            -- squares of
>                   $ [1..]              -- natural numbers
> -k

Hmm. My 0.03$ (to whole thread):

1. I prefer the concept of pipeline.
 - It gives me feeling that I'm not interested in the order of
computation (map all values to square, then filter the odds) but rather
with semi-parallel computation (which is really what is happening).
Let syntax, being much more flexible, may give semi-imperative approach
(although much more mixed).

 - I read that average human remembers up to 7-10 things in short term
memory - why garbage it with variables?

On the other hand more complex computation may require let/where and/or
arrows helper functions. For example:

filter (\x -> case x of Nil -> False; _ -> True) ...
filter (\x -> case x of
          Nil -> False
          _ -> True) ...

is less clear then

filter (not . isNil) ...
where isNil Nil = True
      isNil _   = False

2. The comments in the above example are too verbose for my taste. It is
like (in imperative program):

x = x + 1; // add 1 to x

Anyone having minimal knowledge about syntax will be able to deduce the
comment directly from the line so why repeat it.


c = ~c | (c && 0xFF000000); // Invert the color in ARGB

Is meaningful comment. There is little information what the line does
and it may happen that the operation must be done efficiently (inner

3. While name should be meaningful (oddSquereSum is not - however it
IMHO is permissible in let/where) if project have documentation and
function is exported it should have documentation. While name is part of
documentation it cannot replace it.
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