How to create a function that checks if a word is a palindrome?

Hello!

I want to create a function that checks if a word is a palindrome (a word that is the same when its read left to right as it is right to left)

function P=palindrome(V)

P=palindrome(V(2:end-1));

if V(1)==V(end)

P=palindrome(V(2:end));

P=true;

elseif numel(V)==1

P=false;

end

end

I keep getting errors that i dont have enough input arguments. Any fixes?

Answer 1

[David Hill]

x='racecar';
isequal(x,flip(x));

[Luqas Lundahl]

yes, i thought of that, however im trying to learn functions and using if statements! thank you anyway

[David Hill]

function P=palindrome(V)
  if numel(V)==1||isempty(V)
    P=1;
  elseif V(1)==V(end)
    P=palindrome(V(2:end-1));
  else
    P=0;
  end

[Luqas Lundahl]

thank you!

Answer 2

[Steven Lord]

A recursive approach, like you've tried to implement, can work but one important aspect of recursion is the base case. This is the case for which you don't recursively call the function. Let's look at your function and think about how it works.

function P=palindrome(V)
P=palindrome(V(2:end-1));

So you (the user) calls the palindrome function.

The palindrome function extracts the part of the input without the first and last element then palindrome (the function) calls palindrome.

The palindrome function extracts the part of the input without the first and last element then palindrome (the function) calls palindrome.

The palindrome function extracts the part of the input without the first and last element then palindrome (the function) calls palindrome.

...

What's your base case? When does this chain of palindrome calling palindrome stop?

I suggest you take a few examples and work through them manually with pencil and paper. Write out the steps you perform to and what tests or decisions you make during the process of identifying whether or not these words or phrases are palindromes. From that see if you can identify a base case that you can detect to break out of the calling chain.

candidates = {'racecar', 'racebar', 'abba', 'palindrome', 'q', ''}

[Luqas Lundahl]

will give it a shot! thank you!