fix: IQuote equatable, remove .NET Standard 2.0

docs/pages/home.md

@@ -73,7 +73,7 @@ See the [guide]({{site.baseurl}}/guide/#content) and the [full list of indicator
 Our [NuGet library](https://www.nuget.org/packages/Skender.Stock.Indicators) directly targets all current frameworks for peak performance, including the .NET Standard for older framework compatibility.
 
 - .NET 8.0, 7.0, 6.0
-- .NET Standard 2.1, 2.0
+- .NET Standard 2.1
 
 The compiled library package is [Common Language Specification (CLS) compliant](https://docs.microsoft.com/en-us/dotnet/standard/common-type-system) and can be used in other programming languages, including Python and everything in the .NET universe.
 

src/Indicators.csproj

@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
   <PropertyGroup>
-    <TargetFrameworks>net8.0;net7.0;net6.0;netstandard2.1;netstandard2.0</TargetFrameworks>
+    <TargetFrameworks>net8.0;net7.0;net6.0;netstandard2.1</TargetFrameworks>
 
     <Authors>Dave Skender</Authors>
     <Product>Stock Indicators for .NET</Product>

src/_common/ObsoleteV3.md

@@ -42,6 +42,8 @@ Items marked with 🚩 require special attention since they will not produc
 
 - all backwards compatible v1 accomodations removed.
 
+- no longer supporting .NET Standard 2.0 for older .NET Framework compatibility.
+
 - 🚩 `IReusableResult.Value` property was changed to non-nullable and returns `double.NaN` instead of `null`
   for incalculable periods.  The standard results (e.g. `EmaResult.Ema`) continue to return `null` for incalculable periods.
 

src/_common/Quotes/Quote.Models.cs

@@ -25,7 +25,7 @@ public record class Quote : IQuote
     public decimal Volume { get; set; }
 
     public bool Equals(IQuote? other)
-    => base.Equals(other);
+      => base.Equals(other);
 }
 
 public abstract class EquatableQuote<TQuote>()
@@ -78,8 +78,8 @@ public bool Equals(TQuote? other)
             && (Volume == other.Volume);
     }
 
-    public static bool operator ==(this, other)
-      // ==(EquatableQuote<TQuote> lhs, EquatableQuote<TQuote> rhs)
+    public static bool operator
+        ==(EquatableQuote<TQuote> lhs, EquatableQuote<TQuote> rhs)
     {
         if (lhs is null)
         {
@@ -96,13 +96,13 @@ public bool Equals(TQuote? other)
         return lhs.Equals(rhs);
     }
 
-    public static bool operator !=(this, other)
-        // !=(EquatableQuote<TQuote> lhs, EquatableQuote<TQuote> rhs)
-        => !(lhs == rhs);
+    public static bool operator
+        !=(EquatableQuote<TQuote> lhs, EquatableQuote<TQuote> rhs)
+          => !(lhs == rhs);
 
     public override int GetHashCode()
-        => throw new ApplicationException("this class does not support GetHashCode");
-        //=> (TickDate, Open, High, Low, Close, Volume).GetHashCode();
+        => HashCode.Combine(
+            TickDate, Open, High, Low, Close, Volume);
 }
 
 internal class QuoteD

tests/indicators/TestBase.cs

@@ -38,6 +38,8 @@ public abstract class SeriesTestBase : TestQuoteBase
     internal readonly DateTime evalDate
         = DateTime.ParseExact("12/31/2018", "MM/dd/yyyy", EnglishCulture);
 
+    // TODO: once caught up, make these abstract instead of virtual
+
     [TestMethod]
     public virtual void Standard()
     {

tests/other/PublicApi.Tests.cs

@@ -17,7 +17,8 @@ internal sealed class MyEma : IResult
     public double? Ema { get; set; }
 }
 
-internal sealed class MyCustomQuote : EquatableQuote<MyCustomQuote>, IQuote
+internal sealed class MyCustomQuote
+    : EquatableQuote<MyCustomQuote>, IQuote
 {
     // redirect inherited base properties
     DateTime ISeries.TickDate => CloseDate;