[Haskell-cafe] Why doesn't this work? (palindrome :: IO)

[Yitzchak Gale]

Brandon Allbery wrote:
>>> > case () of
>>> >   () | s == reverse s -> putStrLn "palindrome"
>>> >   _                   -> putStrLn "nope"

Tom Murphy wrote:
>> This is kind of a hack of case, though. I think what the OP was looking
>> for is
>>  isPalindrome word
>>   | (word == reverse word) = putStrLn (word ++ " is a palindrome")
>>   | otherwise              = putStrLn (word ++ " is not a palindrome")

> Erm?  It's as much of a hack of case as yours is, since the above is
> actually using case.

I agree with Tom here. While it's true that the compiler
internally desugars to case, that low-level compiler
transformation doesn't have much to do with the
best way to write clear code.

I find that case often creates code that is more
confusing and bug-prone. Except when what I
really want to express is pattern matching, *and*
there is some specific reason here why I don't
want to use a named function in a let or where
binding. Altogether, it doesn't come up very often
for me.

And even for styles that use case more than I
do, certainly there is room to call the use of
the "case ()" idiom a hack. (Even though I'll
admit that I do use it sometimes.)

Regards,
Yitz