Merge pull request #25 from polyadic/remove-zero

Remove zero
polyadic · Sep 12, 2023 · 0776f3d · 0776f3d
2 parents 9909c9f + a55d87e
commit 0776f3d
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Showing 5 changed files with 16 additions and 47 deletions.
diff --git a/Funcky.Money.Test/MoneyTest.cs b/Funcky.Money.Test/MoneyTest.cs
@@ -1,4 +1,5 @@
 using System.Collections;
+using System.Globalization;
 using FsCheck;
 using FsCheck.Xunit;
 using Xunit;
@@ -172,21 +173,6 @@ public void WeCanDefineMoneyExpressionsWithOperators()
         Assert.Equal(Money.USD(30), product.Evaluate());
     }
 
-    [Property]
-    public Property TheMoneyNeutralElementWorksWithAnyCurrency(Money money)
-    {
-        return (money == (money + Money.Zero).Evaluate()
-                && (money == (Money.Zero + money).Evaluate())).ToProperty().When(!money.IsZero);
-    }
-
-    [Property]
-    public Property InASumOfMultipleZerosWithDifferentCurrenciesTheEvaluationHasTheSameCurrencyAsTheFirstMoneyInTheExpression(Currency c1, Currency c2, Currency c3)
-    {
-        var sum = new Money(0m, c1) + new Money(0m, c2) + new Money(0m, c3) + new Money(0m, c2);
-
-        return (sum.Evaluate().Currency == c1).ToProperty();
-    }
-
     [Fact]
     public void MoneyFormatsCorrectlyAccordingToTheCurrency()
     {
@@ -302,19 +288,6 @@ public void WeCanDelegateTheExchangeRatesToABank()
         Assert.Equal(30m, sum.Evaluate(OneToOneContext(Currency.CHF)).Amount);
     }
 
-    [Fact]
-    public void EvaluationOnZeroMoneysWorks()
-    {
-        var sum = (Money.Zero + Money.Zero) * 1.5m;
-
-        var context = OneToOneContext(Currency.JPY);
-
-        Assert.True(Money.Zero.Evaluate(context).IsZero);
-        Assert.True(sum.Evaluate(context).IsZero);
-        Assert.True(Money.Zero.Evaluate().IsZero);
-        Assert.True(sum.Evaluate().IsZero);
-    }
-
     [Fact]
     public void DifferentPrecisionsCannotBeEvaluatedWithoutAnEvaluationContext()
     {
@@ -479,7 +452,7 @@ public void DividingTwoMoneysWithDifferentCurrenciesNeedAnEvaluationContext()
     [Fact]
     public void DividingTwoMoneysOnlyWorksIfTheDivisorIsNonZero()
     {
-        Assert.Throws<DivideByZeroException>(() => Money.CHF(5) / Money.Zero);
+        Assert.Throws<DivideByZeroException>(() => Money.CHF(5) / Money.CHF(0.0m));
         Assert.Throws<DivideByZeroException>(() => Money.USD(3).Divide(Money.USD(0)));
     }
 

diff --git a/Funcky.Money/Funcky.Money.csproj b/Funcky.Money/Funcky.Money.csproj
@@ -5,8 +5,9 @@
         <Product>Funcky.Money</Product>
         <Description>Funcky.Money is based on Kent Beck's TDD exercise but with more features.</Description>
         <PackageTags>Functional Money</PackageTags>
+        <PackageReadmeFile>README.md</PackageReadmeFile>
         <IsPackable>true</IsPackable>
-        <Version>1.2.0</Version>
+        <Version>1.3.0</Version>
     </PropertyGroup>
     <ItemGroup>
         <InternalsVisibleTo Include="$(AssemblyName).Test" />
@@ -19,6 +20,14 @@
         <PackageReference Include="Funcky.DiscriminatedUnion" PrivateAssets="all" />
         <PackageReference Include="IsExternalInit" PrivateAssets="all" />
     </ItemGroup>
+
+    <ItemGroup>
+        <None Include="..\README.md">
+            <Pack>True</Pack>
+            <PackagePath>\</PackagePath>
+        </None>
+    </ItemGroup>
+
     <ItemGroup>
         <ProjectReference Include="..\Funcky.Money.SourceGenerator\Funcky.Money.SourceGenerator.csproj" OutputItemType="Analyzer" ReferenceOutputAssembly="false" />
     </ItemGroup>

diff --git a/Funcky.Money/Money.cs b/Funcky.Money/Money.cs
@@ -8,8 +8,6 @@ namespace Funcky;
 [DebuggerDisplay("{Amount} {Currency.AlphabeticCurrencyCode,nq}")]
 public sealed partial record Money : IMoneyExpression
 {
-    public static readonly Money Zero = new(0m);
-
     public Money(decimal amount, Option<Currency> currency = default)
     {
         Amount = amount;

diff --git a/Funcky.Money/Visitors/MoneyBag.cs b/Funcky.Money/Visitors/MoneyBag.cs
@@ -7,7 +7,6 @@ internal sealed class MoneyBag
 {
     private readonly Dictionary<Currency, List<Money>> _currencies = new();
     private Option<IRoundingStrategy> _roundingStrategy;
-    private Option<Currency> _emptyCurrency;
 
     public MoneyBag(Money money)
     {
@@ -39,18 +38,8 @@ public Money CalculateTotal(Option<MoneyEvaluationContext> context)
 
     private void Add(Money money)
     {
-        if (money.IsZero)
-        {
-            if (_currencies.None())
-            {
-                _emptyCurrency = money.Currency;
-            }
-        }
-        else
-        {
-            CreateMoneyBagByCurrency(money.Currency);
-            _currencies[money.Currency].Add(money);
-        }
+        CreateMoneyBagByCurrency(money.Currency);
+        _currencies[money.Currency].Add(money);
     }
 
     private static List<Money> MultiplyBag(decimal factor, IEnumerable<Money> bag)
@@ -74,7 +63,7 @@ private Money AggregateSingleMoneyBag()
         => _currencies
             .SingleOrNone() // Single or None throws an InvalidOperationException if we have more than one currency in the Bag
             .Match(
-                none: () => _emptyCurrency.Match(Money.Zero, c => Money.Zero with { Currency = c }),
+                none: () => throw new Exception("nothing to Aggregate"),
                 some: m => CheckAndAggregateBag(m.Value));
 
     private Money CheckAndAggregateBag(IEnumerable<Money> bag)

diff --git a/README.md b/README.md
@@ -85,7 +85,6 @@ These is the evolving list of TDD requirements which led to the implementation.
 * [x] Every construction of `Money` currently rounds to two digits, while this is interesting for 5.7f, it has bad effects in evaluation. We should remove the rounding again.
 * [x] The default `MidpointRounding` mechanism is bankers rounding (`MidpointRounding.ToEven`).
 * [x] Multiply a `Money` with a real number (`int`, and `decimal`).
-* [x] There is a neutral `Money` element (`Zero`).
 * [x] Distribute `Money` equally into n slices (1CHF into 3 slices: [0.33, 0.33, 0.34]).
 * [x] Distribute `Money` proportionally (1 CHF in 1:5 -> [0.17, 0.83]).
 * [x] Extract distribution of money into a strategy which is injected.
@@ -121,6 +120,7 @@ These is the evolving list of TDD requirements which led to the implementation.
 * We prepare a distribution strategy but do not make it chosable at this point.
 * We support the following operators: unary + and -, and the binary operators ==, !=, +, -, * and /.
 * You can divide two different currencies only with the `Divide(IMoneyExpression, IMoneyExpression, Option<MoneyEvaluationContext>)` method where you have to give a `MoneyEvaluationContext` with the necessary exchange rates.
+* We removed the neutral `Money` element (`Zero`), there are too many unsolved problems. If we add it again we should probaly make a NeutralElement : `IMoneyExpression`.
 
 ### Open Decisions