Yet Another Project Euler Series (YAPES) continues with problem four:

A palindromic number reads the same both ways. The largest palindrome made from the product of two 2-digit numbers is 9009 = 91 × 99.

Find the largest palindrome made from the product of two 3-digit numbers.

The most straightforward way to determine if a number is palindromic is to convert it to a string and compare that string with its reverse. Sound easy? It is!

One minor snag is the lack of a library function in F# for reversing strings, but that's easily defined like so:

With String.rev in place, writing an isPalindrome function is trivial.

Using a list comprehension, we can generate all of the palindromes that are products of 3-digit numbers. Once we have this list, producing the result is as simple as passing it to the toLargest function that we defined for Problem Three.

Short and sweet—my favorite!