/**
* Applies an expression to each item in an array and returns an array with
* the applied results.
*
* @see http://docs.mongodb.org/manual/reference/operator/aggregation/map/
* @see Expr::map
* @param mixed|Expr $input An expression that resolves to an array.
* @param string $as The variable name for the items in the input array. The in expression accesses each item in the input array by this variable.
* @param mixed|Expr $in The expression to apply to each item in the input array. The expression accesses the item by its variable name.
* @return self
*/
public function map($input, $as, $in)
{
$this->expr->map($input, $as, $in);
return $this;
}
