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Diffstat (limited to 'Ix/NET/System.Interactive/EnumerableEx.Imperative.cs')
| -rw-r--r-- | Ix/NET/System.Interactive/EnumerableEx.Imperative.cs | 156 |
1 files changed, 156 insertions, 0 deletions
diff --git a/Ix/NET/System.Interactive/EnumerableEx.Imperative.cs b/Ix/NET/System.Interactive/EnumerableEx.Imperative.cs new file mode 100644 index 0000000..fff3927 --- /dev/null +++ b/Ix/NET/System.Interactive/EnumerableEx.Imperative.cs @@ -0,0 +1,156 @@ +// 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); + } + } +} |