51 lines
1.1 KiB
C#
51 lines
1.1 KiB
C#
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using System;
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using System.Collections.Generic;
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namespace Mono.Rocks
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{
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public static class KeyValuePair
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{
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public static KeyValuePair<TKey, TValue>? Just<TKey, TValue> (TKey key, TValue value)
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{
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return new KeyValuePair<TKey, TValue> (key, value);
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}
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}
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public static class Sequence
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{
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public static IEnumerable<TResult> Unfoldr<TSource, TResult> (TSource value, Func<TSource, KeyValuePair<TResult, TSource>?> func)
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{
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return CreateUnfoldrIterator (value, func);
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}
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private static IEnumerable<TResult> CreateUnfoldrIterator<TSource, TResult> (TSource value, Func<TSource, KeyValuePair<TResult, TSource>?> func)
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{
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KeyValuePair<TResult, TSource>? r;
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while ((r = func (value)).HasValue) {
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KeyValuePair<TResult, TSource> v = r ?? new KeyValuePair<TResult, TSource> ();
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yield return v.Key;
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value = v.Value;
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}
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}
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}
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class Test
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{
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public static int Main ()
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{
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IEnumerable<int> x = Sequence.Unfoldr (10, b => b == 0
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? null
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: KeyValuePair.Just (b, b - 1));
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int i = 10;
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foreach (int e in x) {
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Console.WriteLine (e);
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if (i-- != e)
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return 1;
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}
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return 0;
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}
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}
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}
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