Problem with a fraction 1/2

Question

This is probably a crazy question. I have a string value of 1/2 and want to use the value of it in an equation however every time I look at its value that should be .5 it is telling me its a 1 as if it is acting like it is being CINT???

Here is my code snippet

            Dim v As String = "1/2"
            Dim vv As Double
            vv = CSng(Val(v))

I do not care if it is a single or double value just as long as it is the right value, what am I missing and I don't even know how long I have been doing this which concerns me.

Thanks in advance and if you can explain how to do this properly I would appreciate.

Thanks

Les

Answer 1

An Int divided by an Int gives an Int...

You can find functions from Google, like :

Fraction To Decimal

Answer 2

Hello,

Add the following code module to your project.

Public Module Utilities
    <Runtime.CompilerServices.Extension>
    Public Function FractionToDouble(ByVal fraction As String) As Double
        Dim result As Double = 0

        If Double.TryParse(fraction, result) Then
            Return result
        End If

        Dim split() As String = fraction.Split(New Char() {" "c, "/"c})

        If split.Length <> 2 AndAlso split.Length <> 3 Then
            Throw New FormatException("Not a valid fraction.")
        End If

        Dim item1 As Integer
        Dim item2 As Integer

        If Integer.TryParse(split(0), item1) AndAlso Integer.TryParse(split(1), item2) Then

            If split.Length = 2 Then
                Return CDbl(item1) / item2
            End If


            Dim item As System.Int32
            If Integer.TryParse(split(2), item) Then
                Return item1 + CDbl(item2) / item
            End If
        End If

        Throw New FormatException("Not a valid fraction.")

    End Function

End Module

Test

Public Class Form1

    Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click

        Dim values() As String = {"3/4", "1/4", "1/2", "2/32"}

        For Each value In values
            Debug.WriteLine($"{value} -> {value.FractionToDouble()}")
        Next

    End Sub

End Class

Results in the for/each are of type Double resulting with

3/4 -> 0.75
1/4 -> 0.25
1/2 -> 0.5
2/32 -> 0.0625

Answer 3

The standard parsing and conversion functions can parse strings like “1” or “0.5”, but it cannot parse expressions like “1/2” or “sin(3)”. You probably need some special expression parser, or write your own (esp. if the expressions are simple). What kind of expressions do you want to parse?

Answer 4

If you want short code, you can also use the Microsoft ScriptControl to parse the expression =>

Dim scriptType = Type.GetTypeFromCLSID(Guid.Parse("0E59F1D5-1FBE-11D0-8FF2-00A0D10038BC"))
Dim objScriptControl As Object = Activator.CreateInstance(scriptType)
objScriptControl.Language = "vbscript"
Dim sExpression As String = "1/2"
Dim objResult As Double = objScriptControl.Eval(sExpression)

Answer 5

Along the same lines as what Karen did but using Nullable of Decimal.

Add this extension.

Public Module NumExts
    ''' <summary>
    ''' convert fraction string to decimal
    ''' </summary>
    ''' <param name="fraction">fraction string</param>
    ''' <returns>nullable of Decimal. no value is error</returns>
    ''' <remarks></remarks>
    <Runtime.CompilerServices.Extension>
    Public Function FractionToDecimal(fraction As String) As Decimal?
        Dim rv As Decimal? 'no value

        If fraction.Contains("/"c) Then

            Dim terms() As String = fraction.Split(New Char() {" "c, "/"c},
                                                    StringSplitOptions.RemoveEmptyEntries)

            If terms.Length = 2 Then
                Dim dividend As Decimal
                Dim divisor As Decimal
                If Decimal.TryParse(terms(0), dividend) AndAlso
                      Decimal.TryParse(terms(1), divisor) Then
                    rv = dividend / divisor
                End If
            End If
        End If
        Return rv
    End Function

End Module

Usage test

        Dim fracs As String
        Dim frac As Decimal? 'nullable

        fracs = "22/7"
        frac = fracs.FractionToDecimal
        If Not frac.HasValue Then
            Stop 'not a fraction
        End If

        fracs = "a / 6"
        frac = fracs.FractionToDecimal
        If Not frac.HasValue Then
            Stop 'not a fraction
        End If

        fracs = "4 / 9"
        frac = fracs.FractionToDecimal
        If Not frac.HasValue Then
            Stop 'not a fraction
        End If

        fracs = "8 / 4"
        frac = fracs.FractionToDecimal
        If Not frac.HasValue Then
            Stop 'not a fraction
        End If