The **`Map()`** method applies a function to each element in an iterable and returns the resulting iterable, of each iteration, to the next function.

>Note: The **Iterator type** in Rust is used to perform much of the functional heavy-lifting. Any Vec of elements can be transformed into an Iterator using either the `iter()` or the `into_iter()` function.

# Syntax
The `map()` can only be applied to iterables. Therefore, to apply the `map()` function to a vector,​ we need to first convert it to an iterable.

# Code
The following examples show how the map function is used. 
* The `.iter()` and `.into_iter()` functions are being used to convert a vector into an iterable. 
* The `.collect()` method consumes the iterator and collects the resulting values into a collection data type.

## Example 1

fn main() {
  let vector = [1, 2, 3];
  let result = vector.iter().map(|x| x * 2).collect::<Vec<i32>>();
  // another way to write the above statement 
  /*let result: Vec<i32> = vector.iter().map(|x| x * 2).collect();*/
  println!("After mapping: {:?}", result);
}

The above code takes each item in the list and multiplies it by $2$.
## Example 2

fn main() {
let mut count = 0;
for pair in vec!['a', 'b', 'c'].into_iter()
                               .map(|single_letter| { count += 1; (single_letter, count) })
                               {
    println!("{:?}", pair);
}
}

Map function in Rust

Applies a function to each iterable element and returns the iterable for next function.