/* Transforming a sequence
   This example implements an extension method Collect, which transforms
   a sequence of type IEnumerable< T > into a sequence of the same type,
   using a lambda expression to specify the transformation of every element.
------------------------------------------------------------*/
using System;
using System.Collections.Generic;


// static class with an extension method Collect, which can be applied to
// IEnumerable< T >
static class Util {
  
  public static IEnumerable< T > Collect< T >(this IEnumerable< T > sequence, Func< T, T > transform) {
    foreach (T elem in sequence) {
      yield return transform(elem);
    }
  }
}


public class A3 {
  
  public static void Main() {
    //-- Squares of integers
    int[] numbers = {1, 2, 3, 4 ,5, 6, 7, 8, 9, 10};
    Console.Write("Squares of ");
    foreach (int i in numbers) Console.Write(i + " ");
    Console.WriteLine();
    Console.Write("=> ");
    
    var result1 = numbers.Collect(x => x * x);
    foreach (int i in result1) Console.Write(i + " ");
    Console.WriteLine();
    Console.WriteLine();
    
    //-- Caesar cipher (message in lower case letters)
    string msg = "a secret message";
    Console.WriteLine("Message:   " + msg);
    Console.Write("Encrypted: ");
    
    var result2 = msg.Collect(ch => {
      if ('a' <= ch && ch <= 'z') {
        return (char) ('a' + ((ch - 'a') + 3) % 26); // move every letter by 3 positions
      } else {
        return ch;
      }
    });
    foreach (char ch in result2) Console.Write(ch);
    Console.WriteLine();
  }
}