microsoft-visualbasic-runtime/Extensions/Math/NumberEqualityComparer.vb

#Region "Microsoft.VisualBasic::96dd3f761a42c567a8614b43094c5bd0, Microsoft.VisualBasic.Core\Extensions\Math\NumberEqualityComparer.vb"

    ' Author:
    ' 
    '       asuka (amethyst.asuka@gcmodeller.org)
    '       xie (genetics@smrucc.org)
    '       xieguigang (xie.guigang@live.com)
    ' 
    ' Copyright (c) 2018 GPL3 Licensed
    ' 
    ' 
    ' GNU GENERAL PUBLIC LICENSE (GPL3)
    ' 
    ' 
    ' This program is free software: you can redistribute it and/or modify
    ' it under the terms of the GNU General Public License as published by
    ' the Free Software Foundation, either version 3 of the License, or
    ' (at your option) any later version.
    ' 
    ' This program is distributed in the hope that it will be useful,
    ' but WITHOUT ANY WARRANTY; without even the implied warranty of
    ' MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    ' GNU General Public License for more details.
    ' 
    ' You should have received a copy of the GNU General Public License
    ' along with this program. If not, see <http://www.gnu.org/licenses/>.



    ' /********************************************************************************/

    ' Summaries:

    '     Class NumberEqualityComparer
    ' 
    '         Properties: DeltaTolerance
    ' 
    '         Constructor: (+2 Overloads) Sub New
    '         Function: (+2 Overloads) Equals, GetHashCode, ToString
    ' 
    ' 
    ' /********************************************************************************/

#End Region

Imports System.Runtime.CompilerServices
Imports stdNum = System.Math

Namespace Math

    ''' <summary>
    ''' 当两个数的误差值的绝对值小于阈值的时候认为两个数字相等
    ''' </summary>
    Public Class NumberEqualityComparer : Implements IEqualityComparer(Of Double)

        Public Property DeltaTolerance As Double

        <MethodImpl(MethodImplOptions.AggressiveInlining)>
        Sub New(tolerance As Double)
            DeltaTolerance = tolerance
        End Sub

        Sub New()
            Call Me.New(0.00001)
        End Sub

        Public Overrides Function ToString() As String
            Return $"|a-b| <= {DeltaTolerance}"
        End Function

        <MethodImpl(MethodImplOptions.AggressiveInlining)>
        Public Overloads Function Equals() As GenericLambda(Of Double).IEquals
            Return AddressOf Equals
        End Function

        <MethodImpl(MethodImplOptions.AggressiveInlining)>
        Public Overloads Function Equals(x As Double, y As Double) As Boolean Implements IEqualityComparer(Of Double).Equals
            Return stdNum.Abs(x - y) <= _DeltaTolerance
        End Function

        <MethodImpl(MethodImplOptions.AggressiveInlining)>
        Public Overloads Function GetHashCode(obj As Double) As Integer Implements IEqualityComparer(Of Double).GetHashCode
            Return obj.GetHashCode
        End Function
    End Class

End Namespace