MoreEnumerableScanTSource(IEnumerableTSource, FuncTSource, TSource, TSource) Method

Performs a scan (inclusive prefix sum) on a sequence of elements.

Definition

Namespace: MoreLinq
Assembly: MoreLinq (in MoreLinq.dll) Version: 3.4.0+b99a6a8cc504caf2d48372fe54a2f8116c59cd0c

C#

public static IEnumerable<TSource> Scan<TSource>(
	this IEnumerable<TSource> source,
	Func<TSource, TSource, TSource> transformation
)

VB

<ExtensionAttribute>
Public Shared Function Scan(Of TSource) ( 
	source As IEnumerable(Of TSource),
	transformation As Func(Of TSource, TSource, TSource)
) As IEnumerable(Of TSource)

C++

public:
[ExtensionAttribute]
generic<typename TSource>
static IEnumerable<TSource>^ Scan(
	IEnumerable<TSource>^ source, 
	Func<TSource, TSource, TSource>^ transformation
)

F#

[<ExtensionAttribute>]
static member Scan : 
        source : IEnumerable<'TSource> * 
        transformation : Func<'TSource, 'TSource, 'TSource> -> IEnumerable<'TSource>

Parameters

source IEnumerableTSource: Source sequence
transformation FuncTSource, TSource, TSource: Transformation operation

Type Parameters

TSource: Type of elements in source sequence

Return Value

IEnumerableTSource
The scanned sequence

Usage Note

In Visual Basic and C#, you can call this method as an instance method on any object of type IEnumerableTSource. When you use instance method syntax to call this method, omit the first parameter. For more information, see Extension Methods (Visual Basic) or Extension Methods (C# Programming Guide).

Remarks

An inclusive prefix sum returns an equal-length sequence where the N-th element is the sum of the first N input elements. More generally, the scan allows any commutative binary operation, not just a sum. The exclusive version of Scan is PreScanTSource(IEnumerableTSource, FuncTSource, TSource, TSource, TSource). This operator uses deferred execution and streams its result.

Example

C#

int[] values = { 1, 2, 3, 4 };
var prescan = values.PreScan((a, b) => a + b, 0);
var scan = values.Scan((a, b) => a + b);
var result = values.EquiZip(scan, ValueTuple.Create);

prescan will yield { 0, 1, 3, 6 }, while scan and result will both yield { 1, 3, 6, 10 }. This shows the relationship between the inclusive and exclusive prefix sum.