Method Scan

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Scan<TSource>(IEnumerable<TSource>, Func<TSource, TSource, TSource>)

Performs a scan (inclusive prefix sum) on a sequence of elements. This operator is similar to Aggregate<TSource>(IEnumerable<TSource>, Func<TSource, TSource, TSource>) except that Scan<TSource>(IEnumerable<TSource>, Func<TSource, TSource, TSource>) returns the sequence of intermediate results as well as the final one.

Declaration
public static IEnumerable<TSource> Scan<TSource>(this IEnumerable<TSource> source, Func<TSource, TSource, TSource> transformation)
Parameters
Type Name Description
IEnumerable<TSource> source

Source sequence
Func<TSource, TSource, TSource> transformation

Transformation operation
Returns
Type Description
IEnumerable<TSource>

The scanned sequence
Type Parameters
Name Description
TSource

Type of elements in source sequence
Remarks

This operator uses deferred execution and streams its result.

Examples

The following code example demonstrates how to execute a post-fix scan on a sequence using Scan.

var sequence = Enumerable.Range(1, 4);

// execute a scan of the sequence
var result = sequence.Scan((a, b) => a + b);

Console.WriteLine(
    "[" +
    string.Join(", ", result) +
    "]");

// This code produces the following output:
// [1, 3, 6, 10]
Exceptions
Type Condition
ArgumentNullException

source or transformation is null.
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Scan<TSource, TState>(IEnumerable<TSource>, TState, Func<TState, TSource, TState>)

Performs a scan (inclusive prefix sum) on a sequence of elements. This operator is similar to Aggregate<TSource, TAccumulate>(IEnumerable<TSource>, TAccumulate, Func<TAccumulate, TSource, TAccumulate>) except that Scan<TSource, TState>(IEnumerable<TSource>, TState, Func<TState, TSource, TState>) returns the sequence of intermediate results as well as the final one.

Declaration
public static IEnumerable<TState> Scan<TSource, TState>(this IEnumerable<TSource> source, TState seed, Func<TState, TSource, TState> transformation)
Parameters
Type Name Description
IEnumerable<TSource> source

Source sequence
TState seed

Initial state to seed
Func<TState, TSource, TState> transformation

Transformation operation
Returns
Type Description
IEnumerable<TState>

The scanned sequence
Type Parameters
Name Description
TSource

Type of elements in source sequence
TState

Type of state
Remarks

This operator uses deferred execution and streams its result.

Examples

The following code example demonstrates how to execute a post-fix scan on a sequence using Scan.

var sequence = Enumerable.Range(1, 4);

// execute a scan of the sequence
var result = sequence
    .Scan(
        "0",
        (a, b) => $"({a} + {b})");

Console.WriteLine(
    "[ \"" +
    string.Join("\", \"", result) +
    "\" ]");

// This code produces the following output:
// [ "0", "(0 + 1)", "((0 + 1) + 2)", "(((0 + 1) + 2) + 3)", "((((0 + 1) + 2) + 3) + 4)" ]
Exceptions
Type Condition
ArgumentNullException

source or transformation is null.