Mark Needham

F# vs C# vs Java: Functional Collection Parameters

with 12 comments

int[] numbers = { 1,2,3,4,5};
for (int number : numbers) {
    System.out.println(f(number));
}
 
private int f(int value) {
    return value*value;
}

new List<int> (new[] {1, 2, 3, 4, 5}.Select(x => x*x)).ForEach(Console.WriteLine);

[1..5] |> List.map (fun x -> x*x) |> List.iter (printfn "%d");;

int[] numbers = { 1,2,3,4,5};
for (int number : numbers) {
    f(number);
}
 
private void f(int value) {
    if(value > 3) {
        System.out.println(value);
    }
}

new List<int> { 1,2,3,4,5}.FindAll(x => x > 3).ForEach(Console.WriteLine);

[1..5] |> List.filter (fun x -> x > 3) |> List.iter (printfn "%d");;

int sum = 0;
int[] numbers = { 1,2,3,4,5};
for (int number : numbers) {
    sum += number;
}
System.out.println(sum);

Console.WriteLine(new[] {1, 2, 3, 4, 5}.Aggregate(0, (accumulator, x) => accumulator + x));

[1..5] |> List.fold_left (+) 0 |> printfn "%d";;

12 Responses to 'F# vs C# vs Java: Functional Collection Parameters'

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1. [...] F# vs C# vs Java: Functional Collection Parameters (Mark Needham) [...]

   

   Dew Drop - January 19, 2009 | Alvin Ashcraft's Morning Dew

   20 Jan 09 at 1:16 am
2. [...] F# vs C# vs Java: Functional Collection Parameters – Mark Needham explores three of the common functional programming collection operations in three languages, Map, Reduce and Filter, comparing the implementation in F# with taht in C# and Java [...]

   

   Reflective Perspective - Chris Alcock » The Morning Brew #268

   20 Jan 09 at 6:16 pm
3. The first extension class I wrote was this:

   public static class IEnumerableExtensions
   {
   public static IEnumerable Each
   (this IEnumerable collection, Func action)
   {
   foreach (T item in collection)
   {
   yield return action(item);
   }
   }

   public static void Each(this IEnumerable collection, Action action)
   {
   foreach (T item in collection)
   {
   action(item);
   }
   }
   }

   This allows you to write the first two C# examples more concisely:

   new[] { 1, 2, 3, 4, 5 }.Select(x => x * x).Each(Console.WriteLine);

   new[] { 1, 2, 3, 4, 5 }.Where(x => x > 3).Each(Console.WriteLine);

   

   Rik Hemsley

   20 Jan 09 at 7:09 pm
4. Looks like the site software removed my angle brackets. I'm sure you can figure out what's missing!

   

   Rik Hemsley

   20 Jan 09 at 7:10 pm
5. Hi Mark.

   I'm a C# guy so I have a few suggestions about the C# code. Here's my solution to the first two methods Map/Filter.

   Enumerable.Range(1, 5).Select(x => x * x).All(x => { Console.WriteLine(x); return true; });
   Console.WriteLine();
   Enumerable.Range(1, 5).Where(x => x > 3).All(x => { Console.WriteLine(x); return true; });

   The little problem with your methods and those of Rik Hemsley posted in comment is that they create a List or int[]. They allocates memory just to iterate over some int values. In C# we can use Enumerable.Range(int start, int end) which is exactly the same as [start..end] in F#. Because IEnumerable doesn't have ForEach, ( and I don't want to have .ToList().ForEach() ) I'm using "my foreach" – combination of All and return true

   For the 3th method I really don't like the Aggregate method extension method of IEnumerable. So with a little bit of cheating we have :

   Console.WriteLine(Enumerable.Range(1, 5).Sum());

   

   

   Petar Petrov

   22 Jan 09 at 6:52 pm
6. map does NOT evaluate a high-order-function, instead map IS a high-order-function as it calls other functions over a structure.

   

   h0tzenpl0tz

   23 Jan 09 at 12:36 am
7. [...] in Java | Tags: scala | by paulosuzart Estava eu vagando pelo meu Google Reader, e encontrei este post falando sobre uma comparação  "for fun" entra Java, C# e F# em alguns aspectos [...]

   

   Scala, Scala, Scala « Codemountain

   23 Jan 09 at 4:45 am
8. Hi Mark, I´ve added some comparation to Scala. Try http://raseablog.blogspot.com/2009/01/scala-scala-scala.html to see. It would be very nice to receive your visit.
   Thanks and congratulations for the simple, but very straight nice post.

   

   Paulo Suzart

   23 Jan 09 at 5:11 am
9. [...] O post do Paulo que eu li, apesar de também estar no blog dele do link acima, foi lido no Blog do RASEA (um projeto OpenSource que ele toca com alguns amigos) e está aqui. Já o post original com os exemplos iniciais, está aqui. [...]

   

   Ruby, Ruby, Ruby! | lucastex.com

   28 Jan 09 at 3:14 am
10. [...] Blog – Mark Needham’s F# vs C# vs Java: Collection Parameters [...]

    

    Rick Minerich's Development Wonderland : Discoveries This Week 01/30/2009

    31 Jan 09 at 5:47 am
11. The problem with the java version is that they don't are functional style. As your f() method does printing the stuff it is just doing a side-effect and not collecting / filtering values.

    I'd rather write those examples as gathering values in a list / colleciton / enumeration / sequence (lazy). (as you stated in your first paragraph on map). That would be much more interesting because the java version for that is much more noisy than the oder languages:

    int[] numbers = { 1,2,3,4,5};
    Collection result=new ArrayList(5);
    for (int number : numbers) {
    result.add(f(number));
    }

    private int f(int value) {
    return value*value;
    }

    Here the groovy version for map:

    1.upto(5).collect{ it*it }
    and clojure
    (map #(* % %) (range 1 5))

    THAT's concise

    If you want to print it directly:
    groovy: 1.upto(5).each{ println it*it }
    clojure: (map #(println (* % %)) (range 1 5))

    Cheers Michael

    

    Michael Hunger

    30 Apr 09 at 10:15 am
12. Please don't confuse people by using vastly different data structures in your example. Java uses an array, C# a doubly-linked list, and F# a singly-list list. Use the same data structure, say array.

    F#:

    [| 1..5 |] |> Array.map (fun x -> x * x) |> Array.iter (printfn "%i")

    

    A

    15 Oct 09 at 6:21 pm

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