timing experiment on bst in haskell - haskell

Question

Hi i am trying to learn haskell and compare its performance to other languages
when i run the following code..
module BST (
Tree,
singletonTree,
insert,
member
) where
import System.IO
import System.IO.Error hiding (try)
import Control.Exception
import Data.Char
import System.CPUTime
--
-- Take the string and convert it to a list of numbers
--
trim = f . f
where f = reverse . dropWhile isSpace
fromDigits = foldl addDigit 0
where addDigit num d = 10*num+d
strToInt str = fromDigits (map digitToInt str)
split_comma "" = []
split_comma input =
let (a,b) = break (\x->x==',') input in
[(trim a)]++(split_comma (drop 1 b))
make_int_list input =map strToInt (split_comma input)
-- end of converting string to integers
data Tree a = EmptyTree | Node a (Tree a)(Tree a) deriving (Show)
singletonTree :: a -> Tree a
singletonTree x = Node x EmptyTree EmptyTree
insert :: Ord a => a -> Tree a -> Tree a
insert x EmptyTree = singletonTree x
insert x (Node root left right)
| x < root = Node root (insert x left) (right)
| x > root = Node root (left) (insert x right)
| x == root = Node root (Node x left EmptyTree) (right)
member :: Ord a => a -> Tree a -> Bool
member x EmptyTree = False
member x (Node n left right)
| x == n = True
| x < n = member x left
| x > n = member x right
---A test function to do the timing
test_func input_list =do
startTime <- getCPUTime
--Note: If you don't use any results haskell won't even run the code
-- if you just mergesrt here (uncomment next line) instead of print
-- return (let tree = foldr insert EmptyTree )
-- then it will always take 0 seconds since it won't actually sort!
let tree = foldr insert EmptyTree input_list
prin(tree)
finishTime <- getCPUTime
return $ fromIntegral (finishTime - startTime) / 1000000000000
main :: IO ()
main = do
inh <- openFile "random_numbers.txt" ReadMode
mainloop inh
hClose inh
--Read in my file and run test_func on input
mainloop :: Handle -> IO ()
mainloop inh =
do input <- try (hGetLine inh)
case input of
Left e ->
if isEOFError e
then return ()
else ioError e
Right inpStr ->
do
let my_list = make_int_list inpStr;
my_time <- test_func my_list
putStrLn ("Execution time in Sections: ")
print(my_time);
return ();
when attempting to run this code i get
Prelude> :load "bst.hs"
[1 of 1] Compiling BST ( bst.hs, interpreted )
bst.hs:83:29: parse error on input `<-'
Failed, modules loaded: none.
i have exhausted my knowledge of haskell. I tried moving the module statements to both before and after the includes but neither help. I have used both the bst and the timing code separately but combined is causing error
random_numbers.txt is a list of comma separated values.

Answer 1

The last do block is not formatted correctly. Here is a diff:
## -78,9 +78,7 ##
then return ()
else ioError e
Right inpStr ->
- do
- let my_list = make_int_list inpStr;
- my_time <- test_func my_list
- putStrLn ("Execution time in Sections: ")
- print(my_time);
- return ();
+ do let my_list = make_int_list inpStr;
+ my_time <- test_func my_list
+ putStrLn("Execution time in Sections: ")
+ print(my_time)
Notes:
I am not using tabs anywhere in the source; I have a feeling your source uses tabs. My advice is to avoid tabs in Haskell source.
You do not need parens to call functions - putStrLn "..." and print my_time will work
Also, prin(tree) earlier should be print(tree) but is more commonly written print tree - the parens are not needed.