Checking for pallindrome in ruby

Non-recursive

def is_palindrome(s)
  s == s.reverse
end

Recursive

def is_palindrome_r(s)
  if s.length <= 1
    true
  elsif s[0] != s[-1]
    false
  else
    is_palindrome_r(s[1..-2])
  end
end

Testing Note that the recursive method is much slower -- using the 2151 character palindrome by Dan Hoey here, we have:

str = "A man, a plan, a caret, [...2110 chars deleted...] a canal--Panama.".downcase.delete('^a-z')
puts is_palindrome(str)    # => true
puts is_palindrome_r(str)  # => true
 
require 'benchmark'
Benchmark.bm do |b|
  b.report('iterative') {10000.times {is_palindrome(str)}}
  b.report('recursive') {10000.times {is_palindrome_r(str)}}
end

output

true
true
               user     system      total        real
iterative  0.062000   0.000000   0.062000 (  0.055000)
recursive 16.516000   0.000000  16.516000 ( 16.562000)