C#•3y ago

❔ ✅ Using a foreach loop on a custom enumerator

I created my own enumerator using the IEnumerator<T> interface but refactored it into a ref struct which can't implement interfaces. How can I use foreach with it? I noticed that Span<T>.Enumerator does this but probably because it's a part of .NET

using System.Numerics;

namespace common_vector_ops;

public ref struct VectorIterator<T> where T : struct
{
    public int Index { get; private set; }
    public int Increment { get; }
    public Span<T> VectorizedSpan { get; }

    public VectorIterator() : this(Span<T>.Empty)
    {
    }

    public VectorIterator(T[] array)
    {
        VectorizedSpan = array.AsSpan();
        Increment = Vector<T>.Count;
        Index = -Increment;
    }

    public VectorIterator(Span<T> span)
    {
        VectorizedSpan = span;
        Increment = Vector<T>.Count;
        Index = -Increment;
    }

    public bool MoveNext()
    {
        Index += Increment;
        return Index <= VectorizedSpan.Length - Increment;
    }

    public void Reset()
    {
        Index = -Increment;
    }

    public Vector<T> Current => new Vector<T>(VectorizedSpan[Index..]);
}

using System.Numerics;

namespace common_vector_ops;

public ref struct VectorIterator<T> where T : struct
{
    public int Index { get; private set; }
    public int Increment { get; }
    public Span<T> VectorizedSpan { get; }

    public VectorIterator() : this(Span<T>.Empty)
    {
    }

    public VectorIterator(T[] array)
    {
        VectorizedSpan = array.AsSpan();
        Increment = Vector<T>.Count;
        Index = -Increment;
    }

    public VectorIterator(Span<T> span)
    {
        VectorizedSpan = span;
        Increment = Vector<T>.Count;
        Index = -Increment;
    }

    public bool MoveNext()
    {
        Index += Increment;
        return Index <= VectorizedSpan.Length - Increment;
    }

    public void Reset()
    {
        Index = -Increment;
    }

    public Vector<T> Current => new Vector<T>(VectorizedSpan[Index..]);
}

using System.Numerics;

namespace common_vector_ops;

public ref struct VectorIterator<T> where T : struct
{
    public int Index { get; private set; }
    public int Increment { get; }
    public Span<T> VectorizedSpan { get; }

    public VectorIterator() : this(Span<T>.Empty)
    {
    }

    public VectorIterator(T[] array)
    {
        VectorizedSpan = array.AsSpan();
        Increment = Vector<T>.Count;
        Index = -Increment;
    }

    public VectorIterator(Span<T> span)
    {
        VectorizedSpan = span;
        Increment = Vector<T>.Count;
        Index = -Increment;
    }

    public bool MoveNext()
    {
        Index += Increment;
        return Index <= VectorizedSpan.Length - Increment;
    }

    public void Reset()
    {
        Index = -Increment;
    }

    public Vector<T> Current => new Vector<T>(VectorizedSpan[Index..]);
}

using System.Numerics;

namespace common_vector_ops;

public ref struct VectorIterator<T> where T : struct
{
    public int Index { get; private set; }
    public int Increment { get; }
    public Span<T> VectorizedSpan { get; }

    public VectorIterator() : this(Span<T>.Empty)
    {
    }

    public VectorIterator(T[] array)
    {
        VectorizedSpan = array.AsSpan();
        Increment = Vector<T>.Count;
        Index = -Increment;
    }

    public VectorIterator(Span<T> span)
    {
        VectorizedSpan = span;
        Increment = Vector<T>.Count;
        Index = -Increment;
    }

    public bool MoveNext()
    {
        Index += Increment;
        return Index <= VectorizedSpan.Length - Increment;
    }

    public void Reset()
    {
        Index = -Increment;
    }

    public Vector<T> Current => new Vector<T>(VectorizedSpan[Index..]);
}

Anton•2/14/23, 3:26 PM

you don't have to

Anton•2/14/23, 3:26 PM

it will work with foreach as is

Anton•2/14/23, 3:27 PM

also make the current property readonly

Anton•2/14/23, 3:28 PM

you have to add GetEnumerator method

AAnton you have to add GetEnumerator method

DaVinkiOP•2/14/23, 3:41 PM

How would I add this to a Span type? It already has a GetEnumerator method which just enumerates over the elements instead which the foreach was using

DDaVinki How would I add this to a Span type? It already has a GetEnumerator method which...

Anton•2/14/23, 6:51 PM

make a wrapper and return that from a method or something

DaVinkiOP•2/15/23, 3:53 AM

I just added the method to the enumerator itself and used that in the foreach, didn't know it worked like that

DDaVinki I just added the method to the enumerator itself and used that in the foreach, d...

Anton•2/15/23, 9:40 AM

yeah you can do it like that, even though it's better to split these up into two types. the enumerable should not contain the state of enumeration, it should be able to produce new enumerators without restrictions

AAnton yeah you can do it like that, even though it's better to split these up into two...

DaVinkiOP•2/15/23, 3:35 PM

What do you reckon it would be called? SpanSpan? SpanEnumeratorWrapper? Seems unnecessary for the user and program to create a new object that lives for 1 method call which just returns another object anyways

DDaVinki What do you reckon it would be called? SpanSpan? SpanEnumeratorWrapper? Seems un...

Anton•2/15/23, 5:42 PM

if you don't need to support getting the enumerator multiple times, then there is no reason

Anton•2/15/23, 5:42 PM

otherwise, name it blahEnumerableblahEnumerable

Anton•2/15/23, 5:42 PM

Accord•2/16/23, 5:47 PM

Was this issue resolved? If so, run

/close

/close

otherwise I will mark this as stale and this post will be archived until there is new activity.

❔ ✅ Using a foreach loop on a custom enumerator

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