Comments on: Functional C#: Writing a ‘partition’ function

By: Philip Schwarz

Philip Schwarz — Thu, 04 Feb 2010 23:45:40 +0000

@Jonas, @Manuel

The following Scala also works:

val (evens,odds) = 0 to 10 partition ( _ % 2 == 0)

By: Rx: MemoizeAll , Jerome Laban

Rx: MemoizeAll , Jerome Laban — Thu, 04 Feb 2010 05:24:36 +0000

[...] exemple concret de problème posé par l’énumération multiple est la création d’un opérateur de partitionnement d’énumérable. Dans l’exemple donné dans cet article, on peut voir que l’énumérable passé en source est [...]

By: Thomas G Mayfield

Thomas G Mayfield — Wed, 03 Feb 2010 21:35:40 +0000

@Naveen, your GroupBy variant assumes that you’ll always have both positive and negative matches. If they all match positive or all match negative, your First and Second will be the same. And checking against an empty set of objects will result in exceptions.

By: Manuel

Manuel — Wed, 03 Feb 2010 15:57:43 +0000

@Jonas Elfström: I’d say some characters are wasted compared to what you get with Scala’s _ placeholder:

// In hypothetical Scala/Ruby hybrid syntax:
evens,odds = (1..10) partition ( _%2==0)

By: Jonas Elfström

Jonas Elfström — Wed, 03 Feb 2010 08:54:48 +0000

@Philip Schwarz, yes and powerful. Had to check out if Ruby has it.

evens,odds=(1..10).partition{|n| n%2==0}

Not a character wasted and still clear (at least for me).

By: Jonas Elfström

Jonas Elfström — Tue, 02 Feb 2010 14:38:07 +0000

Apart from the multiple variable assignment, couldn’t this be considered a kind of GroupBy?

var evensAndOdds = Enumerable.Range(1, 10).GroupBy(n => n%2==0);

or something like

By: Matt Warren

Matt Warren — Tue, 02 Feb 2010 11:25:23 +0000

@Manuel, yeah it does see http://blogs.msdn.com/bclteam/archive/2009/07/07/building-tuple-matt-ellis.aspx for more info. But I guess this code is from a .NET 3.5 project.

By: The Morning Brew - Chris Alcock » The Morning Brew #530

The Morning Brew - Chris Alcock » The Morning Brew #530 — Tue, 02 Feb 2010 08:41:14 +0000

[...] Functional C#: Writing a ‘partition’ function – Mark Needham continues his series looking at writing more functional code in C# with a look at the implementation of a partition function to allow collections to be split. [...]

By: Manuel

Manuel — Tue, 02 Feb 2010 08:30:56 +0000

I thought the new version of .NET (4.0) had tuples?

By: Naveen

Naveen — Tue, 02 Feb 2010 04:23:58 +0000

I guess this is more Succinct.

public static Tuple Partition(this IEnumerable enumerableOf, Func predicate)
{
var partitioned = enumerableOf.GroupBy(predicate).Select(e => new {e.Key, e});
return new Tuple(partitioned.First().e, partitioned.Last().e);
}