feat: add new indicators (Decay, Edecay, MinusDi, MinusDm, PlusDi, PlusDm, Maxindex, Minindex, Sarext) and update pine scripts, core libs, validation tests, and python bindings

lib/dynamics/minusdi/MinusDi.cs

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+using System.Runtime.CompilerServices;
+
+namespace QuanTAlib;
+
+/// <summary>
+/// MINUS_DI: Minus Directional Indicator (Wilder, 1978)
+/// </summary>
+/// <remarks>
+/// Measures downward directional movement as a percentage of true range.
+/// Extracted from the DX calculation: -DI = Smoothed(-DM) / Smoothed(TR) × 100.
+/// Range: 0 to 100. Higher values indicate stronger downward movement.
+/// </remarks>
+[SkipLocalsInit]
+public sealed class MinusDi : ITValuePublisher
+{
+    private readonly Dx _dx;
+
+    /// <summary>Display name for the indicator.</summary>
+    public string Name { get; }
+
+    public event TValuePublishedHandler? Pub;
+
+    /// <summary>Current -DI value.</summary>
+    public TValue Last { get; private set; }
+
+    /// <summary>True when the indicator has warmed up.</summary>
+    public bool IsHot => _dx.IsHot;
+
+    /// <summary>Bars required for warmup.</summary>
+    public int WarmupPeriod => _dx.WarmupPeriod;
+
+    /// <summary>The period parameter.</summary>
+    public int Period => _dx.Period;
+
+    /// <summary>
+    /// Creates MinusDi with specified period.
+    /// </summary>
+    /// <param name="period">Wilder smoothing period (must be &gt; 0)</param>
+    public MinusDi(int period = 14)
+    {
+        if (period <= 0)
+        {
+            throw new ArgumentException("Period must be greater than 0", nameof(period));
+        }
+        _dx = new Dx(period);
+        Name = $"MinusDi({period})";
+    }
+
+    /// <summary>
+    /// Creates MinusDi and immediately processes the bar series.
+    /// </summary>
+    public MinusDi(TBarSeries source, int period = 14) : this(period)
+    {
+        var result = Batch(source, period);
+        Last = result[^1];
+    }
+
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    public TValue Update(TBar input, bool isNew = true)
+    {
+        _dx.Update(input, isNew);
+        Last = _dx.DiMinus;
+        if (isNew)
+        {
+            Pub?.Invoke(this, new TValueEventArgs { Value = Last, IsNew = isNew });
+        }
+        return Last;
+    }
+
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    public TValue Update(TValue input, bool isNew = true)
+    {
+        // DI requires OHLC data — scalar update not meaningful
+        return Last;
+    }
+
+    public TSeries Update(TBarSeries source)
+    {
+        var result = new TSeries(source.Count);
+        foreach (var bar in source)
+        {
+            result.Add(Update(bar));
+        }
+        return result;
+    }
+
+    /// <summary>
+    /// Initializes the indicator state using the provided bar series history.
+    /// </summary>
+    public void Prime(TBarSeries source)
+    {
+        foreach (var bar in source)
+        {
+            Update(bar);
+        }
+    }
+
+    public void Prime(ReadOnlySpan<double> source, TimeSpan? step = null)
+    {
+        // Not applicable — DI requires OHLC bar data, not scalar values
+    }
+
+    public static TSeries Batch(TBarSeries source, int period = 14)
+    {
+        var indicator = new MinusDi(period);
+        return indicator.Update(source);
+    }
+
+    public static (TSeries Results, MinusDi Indicator) Calculate(TBarSeries source, int period = 14)
+    {
+        var indicator = new MinusDi(period);
+        return (indicator.Update(source), indicator);
+    }
+
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    public void Reset()
+    {
+        _dx.Reset();
+        Last = default;
+    }
+}

lib/dynamics/minusdi/MinusDi.md

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+# MINUS_DI: Minus Directional Indicator
+
+### TL;DR
+Measures downward directional movement strength as a percentage (0-100).
+
+## Introduction
+The Minus Directional Indicator (-DI) measures the strength of downward price movement relative to the true range. It is one of the components of the Directional Movement System developed by J. Welles Wilder Jr.
+
+When -DI is rising, downward price pressure is increasing. When -DI crosses above +DI, it signals a potential bearish trend. The -DI line is commonly plotted alongside +DI to visualize directional balance.
+
+## Calculation
+-DI = Smoothed(-DM) / Smoothed(TR) × 100
+
+Where:
+- -DM (Minus Directional Movement) = max(PrevLow - Low, 0) when PrevLow - Low > High - PrevHigh, else 0
+- TR (True Range) = max(High - Low, |High - PrevClose|, |Low - PrevClose|)
+- Smoothing uses Wilder's method: Smooth = Smooth - Smooth/N + Input
+
+## Parameters
+| Parameter | Default | Range | Description |
+| :--- | :--- | :--- | :--- |
+| Period | 14 | 2-∞ | Wilder smoothing period |
+
+## Interpretation
+- **Rising -DI:** Strengthening downward movement
+- **-DI > +DI:** Bears dominate; potential downtrend
+- **-DI crossover above +DI:** Bearish signal
+- **High -DI (>40):** Strong downward momentum
+
+## References
+- Wilder, J. Welles Jr. "New Concepts in Technical Trading Systems" (1978)