Compare "Guessing Game" in The Rust Guide http://doc.rust-lang.org/guide.html#guessing-game

guess.hs

import           Control.Applicative
import           Control.Exception
import           System.Random
import           Text.Read

main :: IO ()
main = go

go :: IO ()
go = do
    putStrLn "Guess the number!"
    secretNumber <- getRandomNumber
    putStrLn $ "The secret number is: " ++ show secretNumber
    putStrLn "Please input your guess."

    line <- strip <$> getLine `catch`
      \e -> error $ "Failed to read line" ++ show (e :: SomeException)

    case (readMaybe line :: Maybe Int) of
      Just n -> case n `compare` secretNumber of
          LT -> putStrLn "Too small!" >> go
          GT -> putStrLn "Too big!" >> go
          EQ -> putStrLn "You win!"
      Nothing -> putStrLn "Please input number" >> go
  where
    getRandomNumber :: IO Int
    getRandomNumber = (+ 1) . (`mod` 100) <$> randomIO
    strip :: String -> String
    strip = reverse . dropWhile (== '\n') . reverse

guess.rb

loop do
  puts "Guess the number!"
  secret_number = rand 100
  puts "The secret number is: #{secret_number}"
  puts "Please input your guess."

  line = gets.strip rescue puts("Failed to read line")
  puts "you guessed: #{line}"
  
  n = begin Integer(line)
      rescue
        puts("Please input number")
        next
      end
  
  if n < secret_number
    puts "too Small!"
  elsif n == secret_number
    puts "You win!"
    exit
  elsif n > secret_number
    puts "Too big!"
  end
end

guess.rs

use std::io;
use std::rand;

fn main() {
    loop {
        println!("Guess the number!");
        let secret_number = (rand::random::<uint>() % 100) + 1;
        println!("The secret number is: {}", secret_number);
        println!("Please input your guess.");
        let input = io::stdin()
            .read_line()
            .ok()
            .expect("failed to read line");

        let input_num: Option<uint> = from_str(input.as_slice().trim());
        let n = match input_num {
            Some(num) => num,
            None => {
                println!("Please input number");
                return
            }
        };

        println!("You guessed: {}", input);

        match cmp(n, secret_number) {
            Less    => println!("Too small!"),
            Greater => println!("Too big!"),
            Equal   => {
                println!("You win!");
                return;
            }
        }
    }
}

fn cmp(a: uint, b: uint) -> Ordering {
    if a < b { Less }
    else if a > b { Greater }
    else { Equal }
}