Any.Chain.md

Any.Chain

Transform nested loops to a single loop

Nested loop

Known nesting times

Example 1: 3 nested loops

foreach (var i in new[] { "A", "B" })
{
    foreach (var j in new[] { "a", "b" })
    {
        foreach (var k in new[] { "1", "2" })
        {
            Console.WriteLine($"{i}, {j}, {k}");
        }
    }
}

A, a, 1
A, a, 2
A, b, 1
A, b, 2
B, a, 1
B, a, 2
B, b, 1
B, b, 2

Unknown nesting times

Example 2: 3 nested loops (Passing through array)

var chain = Any.Chain(new[]
{
    new[] { "A", "B" },
    new[] { "a", "b" },
    new[] { "1", "2" },
})
    .Where(x => x.Origin == ChainOrigin.Current);

foreach (var iterator in chain)
{
    var (i, j, k) = iterator.Iterators;
    Console.WriteLine($"{i}, {j}, {k}");
}

Different from Nested Loop, Iterators in ChainIterator contains all traversal values (arrays).

This means we can handle nested loops in the same way.

The actual situation may be more complicated, but they have the same characteristics:

• Data processing is usually in the innermost layer, because the innermost layer has all the iteration values.
• Other layers may do some special processing, so you need to know exactly when each layer starts and ends.

Example 3: More complex 3 nested loops

foreach (var i in new[] { "A", "B" })
{
    // Origin = Begin, Cursor = 0
    Console.WriteLine($"Begin: {i}, ,");
    foreach (var j in new[] { "a", "b" })
    {
        // Origin = Begin, Cursor = 1
        Console.WriteLine($"Begin: {i}, {j},");
        foreach (var k in new[] { "1", "2" })
        {
            // Origin = Current, Cursor = 2
            Console.WriteLine($"{i}, {j}, {k}");
        }
        // Origin = End, Cursor = 1
        Console.WriteLine($"End: {i}, {j},");
    }
    // Origin = End, Cursor = 0
    Console.WriteLine($"End: {i}, ,");
}

Example 4: More complex 3 nested loops (Any.Chain)

var chain = Any.Chain(new[]
{
    new[] { "A", "B" },
    new[] { "a", "b" },
    new[] { "1", "2" },
});

foreach (var iterator in chain)
{
    var (i, j, k) = iterator.Iterators;

    if (iterator.Origin == ChainOrigin.Begin)
    {
        Console.WriteLine($"Begin: {i}, {j},");
    }
    else if (iterator.Origin == ChainOrigin.Current)
    {
        Console.WriteLine($"{i}, {j}, {k}");
    }
    else if (iterator.Origin == ChainOrigin.End)
    {
        Console.WriteLine($"End: {i}, {j},");
    }
}

Begin: A, ,
Begin: A, a,
A, a, 1
A, a, 2
End: A, a,
Begin: A, b,
A, b, 1
A, b, 2
End: A, b,
End: A, ,
Begin: B, ,
Begin: B, a,
B, a, 1
B, a, 2
End: B, a,
Begin: B, b,
B, b, 1
B, b, 2
End: B, b,
End: B, ,

Dynamically generate nested

Generate iterators for each level in turn from the seed value.

Example 5: multiplication table

var chain = Any.Chain(9, new Func<int, IEnumerable<int>>[]
{
    s => new int[s].Let(i => i + 1),
    i => new int[i].Let(j => j + 1),
});

foreach (var iterator in chain)
{
    var (i, j) = iterator.Iterators;

    if (iterator.Origin == ChainOrigin.Current)
    {
        Console.Write($"{i}x{j}  ");
    }
    else if (iterator.Origin == ChainOrigin.End)
    {
        Console.WriteLine();
    }
}

1x1
2x1 2x2
3x1 3x2 3x3
4x1 4x2 4x3 4x4
5x1 5x2 5x3 5x4 5x5
6x1 6x2 6x3 6x4 6x5 6x6
7x1 7x2 7x3 7x4 7x5 7x6 7x7
8x1 8x2 8x3 8x4 8x5 8x6 8x7 8x8
9x1 9x2 9x3 9x4 9x5 9x6 9x7 9x8 9x9