Follow these steps to get through this recipe:

1. Create a file named sample_map_result.rs and open it in your text editor.
2. Write the code header with the relevant information:

        //-- #########################
        //-- Task: Implementing map for Result 
        //-- Author: Vigneshwer.D
        //-- Version: 1.0.0
        //-- Date: 26 March 17
        //-- #########################

3. Call the standard library:

      use std::num::ParseIntError;

4. Create a function named double_number that will accept the str input and return a Result<T> type:

        fn double_number(number_str: &str) -> Result<i32,
        ParseIntError> {
          match number_str.parse::<i32>() {
            Ok(n) => Ok(2 * n),
            Err(e) => Err(e),
          }
        }

5. Create a function named double_number_map that will accept the str input and return a Result<T> type:

        fn double_number_map(number_str: &str) -> Result<i32,
        ParseIntError> {
          number_str.parse::<i32>().map(|n| 2 * n)
        }

6. Create a function named print that will accept a Result<T> type as input:

        fn print(result: Result<i32, ParseIntError>) {
          match result {
          Ok(n) => println!("n is {}", n),
          Err(e) => println!("Error: {}", e),
          }
        }

7. Define the main function and declare different input for different functions:

        fn main() {
          // This still presents a reasonable answer.
          let twenty = double_number("10");
          print(twenty);

          // The following now provides a much more helpful
          error message.
          let tt = double_number_map("t");
          print(tt);
        }

You will get the following output upon successful execution of the code: