Re: [Haskell-cafe] Code walking off the right edge of the screen

20 Jun 2009

      Antoine Latter wrote:
...
On Sat, Jun 20, 2009 at 1:05 PM, Deniz Dogan wrote:
...
I (too) often find myself writing code such as this:
if something
 then putStrLn "howdy there!"
 else if somethingElse
         then putStrLn "howdy ho!"
         else ...
I recall reading some tutorial about how you can use the Maybe monad
if your code starts looking like this, but as you can see, that
doesn't really apply here. "something" and "somethingElse" are simply
booleans and each of them have different actions to take if either of
them is True.
So how do I make code like this prettier?
I'm not entirely sure if this is haskell'98, but GHC seems to support
this sort of layout:
main = do
  <some computation>
if something then someOtherComputation else do
<continue at the same indentation>
<<<<<
IMHO, this is ugly and counterintuitive; I like having a single "point
of exit" (to use an imperative programming term) of a function. Your
suggestion is equivalent to

someComputation;
if something then begin
	someOtherComputation;
	exit;
end;
more;

in, say, Pascal. This obscures the fact that "more;" is sometimes/often
not executed. (You could argue the same about exceptions, but they are a
necessary evil ;-).

Regards,

-- 
Jochem Berndsen | jochem@functor.nl
GPG: 0xE6FABFAB