Add a standard key strategy for maps without prefixe

Remove the stupid "next" field

PersistentMap/KeyStrategies.cs

@@ -13,14 +13,45 @@ public interface IKeyStrategy<K>
 {
     int Compare(K x, K y);
     long GetPrefix(K key);
-    
+
     bool UsesPrefixes => true;
-    
+
     // 
     bool IsLossless => false;
 }
 
 
+/// <summary>
+/// A universal key strategy for any type that relies on standard comparisons 
+/// (IComparable, IComparer, or custom StringComparers) without SIMD prefixes.
+/// </summary>
+public readonly struct StandardStrategy<K> : IKeyStrategy<K>
+{
+    private readonly IComparer<K> _comparer;
+
+    // If no comparer is provided, it defaults to Comparer<K>.Default
+    // which automatically uses IComparable<K> if the type implements it.
+    public StandardStrategy(IComparer<K>? comparer = null)
+    {
+        _comparer = comparer ?? Comparer<K>.Default;
+    }
+
+    // Tell the B-Tree to skip SIMD routing and just use LinearSearch
+    public bool UsesPrefixes => false;
+
+    // This will never be called because UsesPrefixes is false, 
+    // but we must satisfy the interface.
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    public long GetPrefix(K key) => 0;
+
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    public int Compare(K x, K y)
+    {
+        return _comparer.Compare(x, y);
+    }
+}
+
+
 public struct UnicodeStrategy : IKeyStrategy<string>
 {
     [MethodImpl(MethodImplOptions.AggressiveInlining)]
@@ -33,17 +64,17 @@ public struct UnicodeStrategy : IKeyStrategy<string>
 
         // 1. Prepare Buffer (8 bytes)
         // stackalloc is virtually free (pointer bump)
-        Span<byte> utf8Bytes = stackalloc byte[8]; 
+        Span<byte> utf8Bytes = stackalloc byte[8];
 
         // 2. Transcode (The "Safe" Magic)
         // This intrinsic handles ASCII efficiently and converts Surrogates/Chinese 
         // into bytes that maintain the correct "Magnitude" (Sort Order).
         // Invalid surrogates become 0xEF (Replacement Char), which sorts > ASCII.
         System.Text.Unicode.Utf8.FromUtf16(
-            key.AsSpan(0, Math.Min(key.Length, 8)), 
-            utf8Bytes, 
-            out _, 
-            out _, 
+            key.AsSpan(0, Math.Min(key.Length, 8)),
+            utf8Bytes,
+            out _,
+            out _,
             replaceInvalidSequences: true); // True ensures we get 0xEF for broken chars
 
         // 3. Load as Big Endian Long
@@ -63,7 +94,7 @@ public struct IntStrategy : IKeyStrategy<int>
 
     [MethodImpl(MethodImplOptions.AggressiveInlining)]
     public long GetPrefix(int key)
-    {  
+    {
         // Pack the 32-bit int into the high 32-bits of the long.
         // This preserves sorting order when scanning the long array.
         // Cast to uint first to prevent sign extension confusion during the shift, 
@@ -92,13 +123,13 @@ public struct DoubleStrategy : IKeyStrategy<double>
         //  -Negative Max -> 0
         //  -0            -> Midpoint
         //  +Negative Max -> Max
-        
+
         long mask = (bits >> 63); // 0 for positive, -1 (All 1s) for negative
-        
+
         // If negative: bits ^ -1 = ~bits (Flip All)
         // If positive: bits ^ 0  = bits (Flip None)
         // Then we toggle the sign bit (0x8000...) to shift the range to signed long.
-        
+
         return (bits ^ (mask & 0x7FFFFFFFFFFFFFFF)) ^ unchecked((long)0x8000000000000000);
     }
 }
@@ -120,7 +151,7 @@ public static class PrefixScanner
         //if (targetPrefix == long.MinValue)
         //{
         //    return 0;
-       //}
+        //}
 
         // Fallback for short arrays or unsupported hardware
         if (!Avx2.IsSupported || prefixes.Length < 4)

PersistentMap/Nodes.cs

@@ -91,7 +91,6 @@ public sealed class LeafNode<K, V> : Node<K>
     
     public K[]? Keys;
     public V[] Values;
-    public LeafNode<K, V>? Next;
 
     internal long[]? _prefixes;
     
@@ -111,9 +110,7 @@ public sealed class LeafNode<K, V> : Node<K>
     {
         Keys = new K[Capacity];
         Values = new V[Capacity];
-        Header.Count = original.Header.Count;
-        Next = original.Next;
-        _prefixes = new long[Capacity];
+        Header.Count = original.Header.Count;        _prefixes = new long[Capacity];
 
         // Copy data
         Array.Copy(original.Keys, Keys, original.Header.Count);
@@ -311,4 +308,4 @@ public readonly struct OwnerId(uint id, ushort gen) : IEquatable<OwnerId>
     {
         return !left.Equals(right);
     }
-}
+}

PersistentMap/Readme.org

@@ -1,4 +1,4 @@
-* NiceBtree (PersistentMap)
+* PersistentMap
 
 A high-performance, persistent (Copy-on-Write) B+ Tree implemented in C#. 
 
@@ -14,6 +14,8 @@ It is designed for zero-overhead reads, SIMD-accelerated key routing, and alloca
 ** When should I use this? 
 Never, probably. This was just a fun little project. If you want a really fast immutable sorted map you should consider it. Despite this map being faster than LanguageExt.HashMap for some key types, you should definitely use that if you don't need a sorted collection. It is well tested and does not have any problems key collisions, which will slow this map down by a lot.
 
+The general version of this, using =StandardStrategy<K>= does not benefit from the prefix optimization.
+
 ** Quick Start
 
 *** 1. Basic Immutable Usage