I just got back from a high-school programming competition where the
only allowed languages were C[++] and Java (*grmbl*). To see just how
cool Haskell is, I'm redoing some of the problems in this more
enlightened language :-)
Anyway, that explains the rather strict requirements for my program's
interface. At one point, the user must enter pairs of numbers like so:
1 4
2 4
3 2
4 1
4 3
0 0
(where two zeros terminate the input). Here is my latest attempt at a
function to do this part of the problem (and it's the easy part ...)
--- snip ---
-- type Player = Int
readIncompatList :: IO [(Player, Player)]
readIncompatList =
readIL' []
where readIL' ans =
do a <- readDec
b <- readDec
if a == 0 && b == 0 then ans else readIL' ((a, b):ans)
--- snip ---
GHC complains with the following:
--- snip ---
prob13.hs:37:
Couldn't match `String -> t' against `[t1]'
Expected type: String -> t
Inferred type: [t1]
Probable cause: `(:)' is applied to too many arguments in the call
((:) (a, b) ans)
In the first argument of `readIL'', namely `((a, b) : ans)'
--- snip ---
Of course, this "probable cause" is ridiculous at face value ... anyway,
my code makes as much sense to me as it can at the moment ... how should
I get it to make sense to GHC? (I couldn't find any examples on
something as mundane as console I/O; funny how people are so fixated on
the real stuff :-) )
Thanks!
Jyrinx
jyrinx_list(a)mindspring.com
