Palindrome detection: Difference between revisions
Add Rhovas solution (string-based unicode safe & character-based)
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WillBAnders (talk | contribs) (Add Rhovas solution (string-based unicode safe & character-based)) |
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=={{header|Rhovas}}==
Simplest solution using <code>String.reverse</code>:
<syntaxhighlight lang="scala">
func isPalindromeReverse(string: String): Boolean {
return string == string.reverse();
}
</syntaxhighlight>
Alternate character-based solution using pattern matching. Unlike <code>String.reverse</code>, this has limited unicode support due to surrogates (code points split into multiple characters).
<syntaxhighlight lang="scala">
func isPalindromeChars(chars: List<String>): Boolean {
match (chars) {
[]: return true;
[elem]: return true;
[first, middle*, last]: return first == last && isPalindromeChars(middle);
}
}
</syntaxhighlight>
Overall result and test cases:
<syntaxhighlight lang="scala">
func isPalindrome(string: String): Boolean {
return isPalindromeReverse(string) && isPalindromeChars(string.chars);
}
assert isPalindrome("");
assert isPalindrome("f");
assert isPalindrome("noon");
assert isPalindrome("kayak");
assert isPalindrome("step on no pets");
assert !isPalindrome("palindrome");
assert !isPalindrome("A man, a plan, a canal - Panama!"); //inexact
assert isPalindrome("§★♖★§"); //single utf16 code points
assert isPalindromeReverse("🗲"); //string reverse handles surrogates
assert !isPalindromeChars("🗲".chars); //.chars splits surrogates into two chars
</syntaxhighlight>
=={{header|Run BASIC}}==
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