Web Development with ReasonML

Writing Recursive Functions

Let’s translate this pseudocode into actual ReasonML code. You use the keyword rec to indicate that a function can be called recursively. Here’s the code for determining if a string is a palindrome, plus some tests.

recursion/palindrome/src/Palindrome.re

let rec isPalindrome = (s: string) : bool => { 
  let len = Js.String.length(s); 
  if (len <= 1) { 
    true;
  } else if (Js.String.get(s, 0) != Js.String.get(s, len - 1)) { 
    false;
  } else {
    isPalindrome(Js.String.slice(~from= 1, ~to_=len - 1, s)); 
  } 
};

Js.log(isPalindrome("civic")); /* output: true */
Js.log(isPalindrome("deed")); /* output: true ...