2012-06-03 Map - 7 higher order functions

2012-06-03 map-7-higher-order-functions

# Title: Map - 7 higher order functions
# Author: Mikael Lundin
# Link: http://blog.mikaellundin.name/2012/06/03/map-7-higher-order-functions.html

Double.cs

private int Double(int i)
{
  return i * 2;
}
 
Map(Double, new [] {1, 2, 3});

Map.cs

public static IEnumerable<U> Map<T, U>(Func<T, U> fn, IEnumerable<T> list)
{
    if (fn == null)
    {
        throw new ArgumentNullException("fn", "Supplied function to Map is not allowed to be null");
    }
 
    if (list == null)
    {
        throw new ArgumentNullException("list", "Supplied list to Map is not allowed to be null");
    }
 
    foreach (var item in list)
    {
        yield return fn(item);
    }
}
 
Map(i => i.ToString(), new[] {1, 2, 3})
-> ["1", "2", "3"]

Select.cs

var people = new[]
{
    new Person { FirstName = "Mikael", Surname = "Lundin" },
    new Person { FirstName = "John", Surname = "Doe" },
    new Person { FirstName = "Foo", Surname = "Bar" },
};
 
var names = people.Select(p => p.FirstName + " " + p.Surname);
 
/*
    => new [] {
        "Mikael Lundin",
        "John Doe",
        "Foo Bar"
    }
*/