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feat: convert DigitalRoot and Mod to generic math

This commit is contained in:
Oliver Booth 2023-04-05 15:35:25 +01:00
parent 87a85b82d9
commit b91aad6305
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GPG Key ID: 20BEB9DC87961025
14 changed files with 101 additions and 3 deletions
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6
X10D.Tests/src/Math/UInt32Tests.cs
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@ -11,8 +11,14 @@ public partial class UInt32Tests
public void DigitalRootShouldBeCorrect()
{
const uint value = 238;
#if NET7_0_OR_GREATER
Assert.AreEqual(4, value.DigitalRoot());
Assert.AreEqual(4, (-value).DigitalRoot());
#else
Assert.AreEqual(4U, value.DigitalRoot());
Assert.AreEqual(4U, (-value).DigitalRoot());
#endif
}
[TestMethod]

8
X10D.Tests/src/Math/UInt64Tests.cs
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@ -11,12 +11,18 @@ public partial class UInt64Tests
public void DigitalRootShouldBeCorrect()
{
const ulong value = 238;
Assert.AreEqual(4U, value.DigitalRoot());
// -ulong operator not defined because it might exceed long.MinValue,
// so instead, cast to long and then negate.
// HAX.
#if NET7_0_OR_GREATER
Assert.AreEqual(4, (-(long)value).DigitalRoot());
Assert.AreEqual(4, value.DigitalRoot());
#else
Assert.AreEqual(4U, (-(long)value).DigitalRoot());
Assert.AreEqual(4U, value.DigitalRoot());
#endif
}
[TestMethod]

4
X10D/src/Math/BigIntegerExtensions.cs
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@ -10,6 +10,7 @@ namespace X10D.Math;
/// </summary>
public static class BigIntegerExtensions
{
#if !NET7_0_OR_GREATER
/// <summary>
/// Computes the digital root of this 8-bit integer.
/// </summary>
@ -27,6 +28,7 @@ public static class BigIntegerExtensions
BigInteger root = BigInteger.Abs(value).Mod(9);
return (int)(root == 0 ? 9 : root);
}
#endif
/// <summary>
/// Returns the factorial of the current 64-bit signed integer.
@ -155,6 +157,7 @@ public static class BigIntegerExtensions
return value * other / value.GreatestCommonFactor(other);
}
#if !NET7_0_OR_GREATER
/// <summary>
/// Performs a modulo operation which supports a negative dividend.
/// </summary>
@ -176,6 +179,7 @@ public static class BigIntegerExtensions
BigInteger r = dividend % divisor;
return r < 0 ? r + divisor : r;
}
#endif
/// <summary>
/// Returns the multiplicative persistence of a specified value.

58
X10D/src/Math/BinaryIntegerExtensions.cs Normal file
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@ -0,0 +1,58 @@
#if NET7_0_OR_GREATER
using System.Diagnostics.Contracts;
using System.Globalization;
using System.Numerics;
using System.Runtime.CompilerServices;
using X10D.CompilerServices;
namespace X10D.Math;
/// <summary>
/// Math-related extension methods for <see cref="IBinaryInteger{TSelf}" />.
/// </summary>
public static class BinaryIntegerExtensions
{
/// <summary>
/// Computes the digital root of this integer.
/// </summary>
/// <param name="value">The value whose digital root to compute.</param>
/// <returns>The digital root of <paramref name="value" />.</returns>
/// <remarks>The digital root is defined as the recursive sum of digits until that result is a single digit.</remarks>
/// <remarks>
/// <para>The digital root is defined as the recursive sum of digits until that result is a single digit.</para>
/// <para>For example, the digital root of 239 is 5: <c>2 + 3 + 9 = 14</c>, then <c>1 + 4 = 5</c>.</para>
/// </remarks>
[Pure]
[MethodImpl(CompilerResources.MethodImplOptions)]
public static int DigitalRoot<TInteger>(this TInteger value)
where TInteger : IBinaryInteger<TInteger>
{
var nine = TInteger.CreateChecked(9);
TInteger root = TInteger.Abs(value).Mod(nine);
return int.CreateChecked(root == TInteger.Zero ? nine : root);
}
/// <summary>
/// Performs a modulo operation which supports a negative dividend.
/// </summary>
/// <param name="dividend">The dividend.</param>
/// <param name="divisor">The divisor.</param>
/// <returns>The result of <c>dividend mod divisor</c>.</returns>
/// <remarks>
/// The <c>%</c> operator (commonly called the modulo operator) in C# is not defined to be modulo, but is instead
/// remainder. This quirk inherently makes it difficult to use modulo in a negative context, as <c>x % y</c> where x is
/// negative will return a negative value, akin to <c>-(x % y)</c>, even if precedence is forced. This method provides a
/// modulo operation which supports negative dividends.
/// </remarks>
/// <author>ShreevatsaR, https://stackoverflow.com/a/1082938/1467293</author>
/// <license>CC-BY-SA 2.5</license>
[Pure]
[MethodImpl(CompilerResources.MethodImplOptions)]
public static TInteger Mod<TInteger>(this TInteger dividend, TInteger divisor)
where TInteger : IBinaryInteger<TInteger>
{
TInteger r = dividend % divisor;
return r < TInteger.Zero ? r + divisor : r;
}
}
#endif

2
X10D/src/Math/ByteExtensions.cs
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@ -9,6 +9,7 @@ namespace X10D.Math;
/// </summary>
public static class ByteExtensions
{
#if !NET7_0_OR_GREATER
/// <summary>
/// Computes the digital root of this 8-bit integer.
/// </summary>
@ -26,6 +27,7 @@ public static class ByteExtensions
int root = value % 9;
return (byte)(root == 0 ? 9 : root);
}
#endif
/// <summary>
/// Returns the factorial of the current 8-bit unsigned integer.

4
X10D/src/Math/Int16Extensions.cs
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@ -9,6 +9,7 @@ namespace X10D.Math;
/// </summary>
public static class Int16Extensions
{
#if !NET7_0_OR_GREATER
/// <summary>
/// Computes the digital root of this 16-bit integer.
/// </summary>
@ -25,6 +26,7 @@ public static class Int16Extensions
short root = System.Math.Abs(value).Mod(9);
return root < 1 ? (short)(9 - root) : root;
}
#endif
/// <summary>
/// Returns the factorial of the current 16-bit signed integer.
@ -125,6 +127,7 @@ public static class Int16Extensions
return (short)((long)value).LowestCommonMultiple(other);
}
#if !NET7_0_OR_GREATER
/// <summary>
/// Performs a modulo operation which supports a negative dividend.
/// </summary>
@ -146,6 +149,7 @@ public static class Int16Extensions
int r = dividend % divisor;
return (short)(r < 0 ? r + divisor : r);
}
#endif
/// <summary>
/// Returns the multiplicative persistence of a specified value.

4
X10D/src/Math/Int32Extensions.cs
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@ -9,6 +9,7 @@ namespace X10D.Math;
/// </summary>
public static class Int32Extensions
{
#if !NET7_0_OR_GREATER
/// <summary>
/// Computes the digital root of this 32-bit integer.
/// </summary>
@ -25,6 +26,7 @@ public static class Int32Extensions
int root = System.Math.Abs(value).Mod(9);
return root < 1 ? 9 - root : root;
}
#endif
/// <summary>
/// Returns the factorial of the current 32-bit signed integer.
@ -125,6 +127,7 @@ public static class Int32Extensions
return (int)((long)value).LowestCommonMultiple(other);
}
#if !NET7_0_OR_GREATER
/// <summary>
/// Performs a modulo operation which supports a negative dividend.
/// </summary>
@ -146,6 +149,7 @@ public static class Int32Extensions
int r = dividend % divisor;
return r < 0 ? r + divisor : r;
}
#endif
/// <summary>
/// Returns the multiplicative persistence of a specified value.

4
X10D/src/Math/Int64Extensions.cs
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@ -9,6 +9,7 @@ namespace X10D.Math;
/// </summary>
public static class Int64Extensions
{
#if !NET7_0_OR_GREATER
/// <summary>
/// Computes the digital root of this 64-bit integer.
/// </summary>
@ -25,6 +26,7 @@ public static class Int64Extensions
long root = System.Math.Abs(value).Mod(9L);
return root < 1L ? 9L - root : root;
}
#endif
/// <summary>
/// Returns the factorial of the current 64-bit signed integer.
@ -164,6 +166,7 @@ public static class Int64Extensions
return value * other / value.GreatestCommonFactor(other);
}
#if !NET7_0_OR_GREATER
/// <summary>
/// Performs a modulo operation which supports a negative dividend.
/// </summary>
@ -185,6 +188,7 @@ public static class Int64Extensions
long r = dividend % divisor;
return r < 0 ? r + divisor : r;
}
#endif
/// <summary>
/// Returns the multiplicative persistence of a specified value.

4
X10D/src/Math/SByteExtensions.cs
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@ -10,6 +10,7 @@ namespace X10D.Math;
[CLSCompliant(false)]
public static class SByteExtensions
{
#if !NET7_0_OR_GREATER
/// <summary>
/// Computes the digital root of this 32-bit integer.
/// </summary>
@ -26,6 +27,7 @@ public static class SByteExtensions
int root = System.Math.Abs(value).Mod(9);
return (sbyte)(root < 1 ? 9 - root : root);
}
#endif
/// <summary>
/// Returns the factorial of the current 8-bit signed integer.
@ -126,6 +128,7 @@ public static class SByteExtensions
return (sbyte)((long)value).LowestCommonMultiple(other);
}
#if !NET7_0_OR_GREATER
/// <summary>
/// Performs a modulo operation which supports a negative dividend.
/// </summary>
@ -147,6 +150,7 @@ public static class SByteExtensions
int r = dividend % divisor;
return (sbyte)(r < 0 ? r + divisor : r);
}
#endif
/// <summary>
/// Returns the multiplicative persistence of a specified value.

2
X10D/src/Math/UInt16Extensions.cs
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@ -10,6 +10,7 @@ namespace X10D.Math;
[CLSCompliant(false)]
public static class UInt16Extensions
{
#if !NET7_0_OR_GREATER
/// <summary>
/// Computes the digital root of the current 16-bit unsigned integer.
/// </summary>
@ -26,6 +27,7 @@ public static class UInt16Extensions
var root = (ushort)(value % 9);
return (ushort)(root == 0 ? 9 : root);
}
#endif
/// <summary>
/// Returns the factorial of the current 16-bit unsigned integer.

2
X10D/src/Math/UInt32Extensions.cs
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@ -10,6 +10,7 @@ namespace X10D.Math;
[CLSCompliant(false)]
public static class UInt32Extensions
{
#if !NET7_0_OR_GREATER
/// <summary>
/// Computes the digital root of the current 32-bit unsigned integer.
/// </summary>
@ -26,6 +27,7 @@ public static class UInt32Extensions
uint root = value % 9;
return root == 0 ? 9 : root;
}
#endif
/// <summary>
/// Returns the factorial of the current 32-bit unsigned integer.

2
X10D/src/Math/UInt64Extensions.cs
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@ -10,6 +10,7 @@ namespace X10D.Math;
[CLSCompliant(false)]
public static class UInt64Extensions
{
#if !NET7_0_OR_GREATER
/// <summary>
/// Computes the digital root of the current 64-bit unsigned integer.
/// </summary>
@ -26,6 +27,7 @@ public static class UInt64Extensions
ulong root = value % 9;
return root == 0 ? 9 : root;
}
#endif
/// <summary>
/// Returns the factorial of the current 64-bit unsigned integer.

2
X10D/src/Time/Int16Extensions.cs
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@ -32,7 +32,7 @@ public static class Int16Extensions
value++;
}
return value.Mod(4) == 0 && (value.Mod(100) != 0 || value.Mod(400) == 0);
return value.Mod((short)4) == 0 && (value.Mod((short)100) != 0 || value.Mod((short)400) == 0);
}
/// <summary>

2
X10D/src/Time/SByteExtensions.cs
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@ -33,7 +33,7 @@ public static class SByteExtensions
value++;
}
return value.Mod(4) == 0 && value.Mod(100) != 0; // mod 400 not required, sbyte.MaxValue is 127 anyway
return value.Mod((sbyte)4) == 0 && value.Mod((sbyte)100) != 0; // mod 400 not required, sbyte.MaxValue is 127 anyway
}
/// <summary>