Why does my code work on Playgrounds but not CoderPad? - swift

Question

I have a very simple func in Xcode playgrounds which works when I run it. But when i try to run the same code in CoderPad it gives me the following error Solution.swift:18:1: warning: result of call to 'isPalindrome(word:)' is unused
isPalindrome(word:"racecar")
Here is the code
import Foundation
func isPalindrome(word: String) -> Bool{
var oddCharacters: Set<Character> = []
for char in word {
if oddCharacters.contains(char){
oddCharacters.remove(char)
}else{
oddCharacters.insert(char)
}
}
return oddCharacters.count <= 1
}
isPalindrome(word:"racecar")
I really do not understand why this is happening.

Answer 1

Try this:
import Foundation
func isPalindrome(word: String) -> Bool{
var oddCharacters: Set<Character> = []
for char in word {
if oddCharacters.contains(char){
oddCharacters.remove(char)
}else{
oddCharacters.insert(char)
}
}
return oddCharacters.count <= 1
}
print(isPalindrome(word:"racecar"))
all you had to do was print it, hope this helped

Answer 2

That means, that the "left-hand-side" result of the call to your function isPalindrome(word: "racecar") is unused ("wasted").
It seems that for a debugging, testing, try-out environment like a Playground it's just okay to find out the result of this call (true) without storing it inside a variable. However, when doing that in other development environments, the compiler will be complaining about that. I can give you four options that would prevent the error from being thrown, just to give you a better idea of why the compiler is complaining:
If you want to use it in your further code below, just store the result and change your calling line to let isPalindrome = isPalindrome(word: "racecar"). But if you don't use it, the compiler will give you a warning again saying that you're never using your isPalindrome variable... --> Option 2
If you don't need the result, you can also just say: _ = isPalindrome(word: "racecar"). That will explicitly tell the compiler "bro, it's okay if the result is just ignored". It wouldn't make much sense for this function, though.
You can add the #discardableResult keyword prior to your function declaration, so it would say: #discardableResult func isPalindrome(word: String) -> Bool { ... That would kinda just silence your thrown error and like option 2 just tell the compiler that it's okay to just ignore the result of this function.
Just use the result in any way like:
if isPalindrome(word: "racecar") {
// do something
} else {
// do something else
}
// or
print("racecar is a palindrome: \(isPalindrome(word: "racecar")")
and everything will just be fine. I hope that helps you!