Talk:Palindrome detection

Spaces and punctuation

The task specification states both:"The function must not ignore spaces and punctuations" and later: "you must make it all the same case and strip spaces".

So ignore or strip spaces - what should be done? --Paddy3118 20:56, 5 December 2008 (UTC)

I think what is meant is that the function itself shouldn't ignore spaces or punctuations, but if using the given example, the test code must remove spaces and convert to either uppercase or lowercase, because otherwise the example isn't a character-wise palindrome. I think it would make more sense to use some example which already is a character-wise palindrome by itself, say the German word "nennen" (to name). --Ce 09:42, 6 December 2008 (UTC)

It is what I've meant... As example of palindrome I used "In girum imus ..." just because it is the longest I know by heart: the "ignore or strip spaces" refers to that example as I wrote there; looking at the code it is clear what I've meant. According to me a function that tests the palindromicity of a "arbitrary" sequence is more general than one that "ignores" by design some characters; you can use the function you wrote to test palindromicity on "In girum imus nocte ...", provided that you strip spaces and make the case of all letters the same... outside the function, e.g. is_palindrome(stripchars(string)), and write stripchars according to any need. In the codes, I did it by hand coding the test string as "ingirumimusnocte...", that is less readable, but in this way I had not to write a stripchars function just to test!

Haskell recursive solution note

I suppose the Haskell recursive code can be written a lot better, but I don't know how. --ShinTakezou 14:08, 5 December 2008 (UTC)

Does this look better to you?

is_palindrome_r x | length x <= 1 = True
                  | head x == last x = is_palindrome_r . tail. init $ x
                  | otherwise = False

--Gaaijz 14:37, 5 December 2008 (UTC)

Yes, if it works, why don't you put it in? I've tested it, it works, put it in instead of mine ;) --ShinTakezou 19:09, 5 December 2008 (UTC)

The Python recursive example isn't testing that the string is a palindrome. It seems to actually be a test for whether the object tested supports len() and slicing. Drea 16:56, 5 December 2008 (UTC)

Why? I am still learning Python... even though there's no type check (right?) I suppose the normal use of such a function is on strings or arrays, both supporting len and slicing; maybe it makes sense to be able to test palindromicity also on other objects. Anyway it worked rather well when tested ;) --ShinTakezou 19:09, 5 December 2008 (UTC)

It looks like the Perl example doesn't check for character equality either. --Mwn3d 16:59, 5 December 2008 (UTC)

Oh my ... yes, thanks (the same as Python... can't remember if I simply forgot or were cut... fixing --ShinTakezou 19:09, 5 December 2008 (UTC)

I've fixed the Python example. I don't know any Perl though, so I'll leave that for someone else. Drea 17:03, 5 December 2008 (UTC)

Oh my ... yes, thanks :) --ShinTakezou 19:09, 5 December 2008 (UTC)

No problem :o) Drea 19:29, 5 December 2008 (UTC)