Sara,

--test function test :: String -> String test s |s == "true" = "True" |s == "false" = "False" |otherwise = []

Then, I run *Test> readMsgFile Input file: test1.txt Output file: result1.txt

The content of test1.txt is string "true". So I expect the result in "result1.txt" is "True" But, open file "result1.txt", it displays empty.

Could it be that the input file has a trailing return or something similar? You could easily test this by making a small change to your test function: test s | ... | ... | otherwise = error $ "The file contains: " ++ s HTH, Stefan

Hi Sara, Just a guess, but your input file is probably "true\n" - with a trailing newline. In fact, many text editors won't let you create a file without that training newline. Thanks Neil On 7/3/06, Sara Kenedy wrote:

Hi all,

I have a module Test.hs:

module Test where import IO readMsgFile = do putStr "Input file: " ifile <- getLine putStr "Output file: " ofile <- getLine s <- readFile ifile writeFile ofile (test s)

--test function test :: String -> String test s |s == "true" = "True" |s == "false" = "False" |otherwise = []

Then, I run *Test> readMsgFile Input file: test1.txt Output file: result1.txt

The content of test1.txt is string "true". So I expect the result in "result1.txt" is "True" But, open file "result1.txt", it displays empty.

I do not know why it does not return correct answer. If you don't mind, please share with me. Thanks a lot.

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