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