157 lines
8.2 KiB
C#
157 lines
8.2 KiB
C#
// Copyright (c) Microsoft Open Technologies, Inc. All rights reserved. See License.txt in the project root for license information.
|
|
using System;
|
|
using System.Collections.Generic;
|
|
using System.Linq;
|
|
using System.Threading;
|
|
|
|
namespace System.Linq
|
|
{
|
|
public static partial class EnumerableEx
|
|
{
|
|
/// <summary>
|
|
/// Generates an enumerable sequence by repeating a source sequence as long as the given loop condition holds.
|
|
/// </summary>
|
|
/// <typeparam name="TResult">Result sequence element type.</typeparam>
|
|
/// <param name="condition">Loop condition.</param>
|
|
/// <param name="source">Sequence to repeat while the condition evaluates true.</param>
|
|
/// <returns>Sequence generated by repeating the given sequence while the condition evaluates to true.</returns>
|
|
public static IEnumerable<TResult> While<TResult>(Func<bool> condition, IEnumerable<TResult> source)
|
|
{
|
|
if (condition == null)
|
|
throw new ArgumentNullException("condition");
|
|
if (source == null)
|
|
throw new ArgumentNullException("source");
|
|
|
|
return WhileCore(condition, source).Concat();
|
|
}
|
|
|
|
static IEnumerable<IEnumerable<TSource>> WhileCore<TSource>(Func<bool> condition, IEnumerable<TSource> source)
|
|
{
|
|
while (condition())
|
|
yield return source;
|
|
}
|
|
|
|
/// <summary>
|
|
/// Returns an enumerable sequence based on the evaluation result of the given condition.
|
|
/// </summary>
|
|
/// <typeparam name="TResult">Result sequence element type.</typeparam>
|
|
/// <param name="condition">Condition to evaluate.</param>
|
|
/// <param name="thenSource">Sequence to return in case the condition evaluates true.</param>
|
|
/// <param name="elseSource">Sequence to return in case the condition evaluates false.</param>
|
|
/// <returns>Either of the two input sequences based on the result of evaluating the condition.</returns>
|
|
public static IEnumerable<TResult> If<TResult>(Func<bool> condition, IEnumerable<TResult> thenSource, IEnumerable<TResult> elseSource)
|
|
{
|
|
if (condition == null)
|
|
throw new ArgumentNullException("condition");
|
|
if (thenSource == null)
|
|
throw new ArgumentNullException("thenSource");
|
|
if (elseSource == null)
|
|
throw new ArgumentNullException("elseSource");
|
|
|
|
return EnumerableEx.Defer(() => condition() ? thenSource : elseSource);
|
|
}
|
|
|
|
/// <summary>
|
|
/// Returns an enumerable sequence if the evaluation result of the given condition is true, otherwise returns an empty sequence.
|
|
/// </summary>
|
|
/// <typeparam name="TResult">Result sequence element type.</typeparam>
|
|
/// <param name="condition">Condition to evaluate.</param>
|
|
/// <param name="thenSource">Sequence to return in case the condition evaluates true.</param>
|
|
/// <returns>The given input sequence if the condition evaluates true; otherwise, an empty sequence.</returns>
|
|
public static IEnumerable<TResult> If<TResult>(Func<bool> condition, IEnumerable<TResult> thenSource)
|
|
{
|
|
if (condition == null)
|
|
throw new ArgumentNullException("condition");
|
|
if (thenSource == null)
|
|
throw new ArgumentNullException("thenSource");
|
|
|
|
return EnumerableEx.Defer(() => condition() ? thenSource : Enumerable.Empty<TResult>());
|
|
}
|
|
|
|
/// <summary>
|
|
/// Generates an enumerable sequence by repeating a source sequence as long as the given loop postcondition holds.
|
|
/// </summary>
|
|
/// <typeparam name="TResult">Result sequence element type.</typeparam>
|
|
/// <param name="source">Source sequence to repeat while the condition evaluates true.</param>
|
|
/// <param name="condition">Loop condition.</param>
|
|
/// <returns>Sequence generated by repeating the given sequence until the condition evaluates to false.</returns>
|
|
public static IEnumerable<TResult> DoWhile<TResult>(this IEnumerable<TResult> source, Func<bool> condition)
|
|
{
|
|
if (source == null)
|
|
throw new ArgumentNullException("source");
|
|
if (condition == null)
|
|
throw new ArgumentNullException("condition");
|
|
|
|
return source.Concat(While(condition, source));
|
|
}
|
|
|
|
/// <summary>
|
|
/// Returns a sequence from a dictionary based on the result of evaluating a selector function.
|
|
/// </summary>
|
|
/// <typeparam name="TValue">Type of the selector value.</typeparam>
|
|
/// <typeparam name="TResult">Result sequence element type.</typeparam>
|
|
/// <param name="selector">Selector function used to pick a sequence from the given sources.</param>
|
|
/// <param name="sources">Dictionary mapping selector values onto resulting sequences.</param>
|
|
/// <returns>The source sequence corresponding with the evaluated selector value; otherwise, an empty sequence.</returns>
|
|
public static IEnumerable<TResult> Case<TValue, TResult>(Func<TValue> selector, IDictionary<TValue, IEnumerable<TResult>> sources)
|
|
{
|
|
if (selector == null)
|
|
throw new ArgumentNullException("selector");
|
|
if (sources == null)
|
|
throw new ArgumentNullException("sources");
|
|
|
|
return Case(selector, sources, Enumerable.Empty<TResult>());
|
|
}
|
|
|
|
/// <summary>
|
|
/// Returns a sequence from a dictionary based on the result of evaluating a selector function, also specifying a default sequence.
|
|
/// </summary>
|
|
/// <typeparam name="TValue">Type of the selector value.</typeparam>
|
|
/// <typeparam name="TResult">Result sequence element type.</typeparam>
|
|
/// <param name="selector">Selector function used to pick a sequence from the given sources.</param>
|
|
/// <param name="sources">Dictionary mapping selector values onto resulting sequences.</param>
|
|
/// <param name="defaultSource">Default sequence to return in case there's no corresponding source for the computed selector value.</param>
|
|
/// <returns>The source sequence corresponding with the evaluated selector value; otherwise, the default source.</returns>
|
|
public static IEnumerable<TResult> Case<TValue, TResult>(Func<TValue> selector, IDictionary<TValue, IEnumerable<TResult>> sources, IEnumerable<TResult> defaultSource)
|
|
{
|
|
if (selector == null)
|
|
throw new ArgumentNullException("selector");
|
|
if (sources == null)
|
|
throw new ArgumentNullException("sources");
|
|
if (defaultSource == null)
|
|
throw new ArgumentNullException("defaultSource");
|
|
|
|
return EnumerableEx.Defer(() =>
|
|
{
|
|
IEnumerable<TResult> result;
|
|
if (!sources.TryGetValue(selector(), out result))
|
|
result = defaultSource;
|
|
return result;
|
|
});
|
|
}
|
|
|
|
/// <summary>
|
|
/// Generates a sequence by enumerating a source sequence, mapping its elements on result sequences, and concatenating those sequences.
|
|
/// </summary>
|
|
/// <typeparam name="TSource">Source sequence element type.</typeparam>
|
|
/// <typeparam name="TResult">Result sequence element type.</typeparam>
|
|
/// <param name="source">Source sequence.</param>
|
|
/// <param name="resultSelector">Result selector to evaluate for each iteration over the source.</param>
|
|
/// <returns>Sequence concatenating the inner sequences that result from evaluating the result selector on elements from the source.</returns>
|
|
public static IEnumerable<TResult> For<TSource, TResult>(IEnumerable<TSource> source, Func<TSource, IEnumerable<TResult>> resultSelector)
|
|
{
|
|
if (source == null)
|
|
throw new ArgumentNullException("source");
|
|
if (resultSelector == null)
|
|
throw new ArgumentNullException("resultSelector");
|
|
|
|
return ForCore(source, resultSelector).Concat();
|
|
}
|
|
|
|
static IEnumerable<IEnumerable<TResult>> ForCore<TSource, TResult>(IEnumerable<TSource> source, Func<TSource, IEnumerable<TResult>> resultSelector)
|
|
{
|
|
return source.Select(resultSelector);
|
|
}
|
|
}
|
|
}
|