'Author:     Eric Heim
'Date Created:  3/30/2011
'Course:        CS0007
'Description:   This program takes a positive whole number from the user and displays that 
'               numbers prime factorization.  If the user does not enter a positive whole number
'               the program displays a message box telling them so.

Option Strict On
Option Explicit On
Option Infer Off

Public Class frmMain

    Private Sub btnSubmit_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnSubmit.Click
        'If the number is a positive whole number 
        If IsPositiveWhole(txtNumber.Text) Then
            'Put the string of prime factors into the factors text box
            txtFactors.Text = FindPrimeFactors(CInt(txtNumber.Text))
        Else
            MessageBox.Show("You did not enter a positive, whole number.", "Invalid Input")
        End If
    End Sub

    'Name:         IsPositiveWhole
    'Parameters:   stringNumber - string to check if its a positive whole number
    'Returns:      Boolean - true if it is a positive, whole number, false if it isn't
    'Description:  Checks to see if the string parameter is a positive whole number
    Function IsPositiveWhole(ByVal stringNumber As String) As Boolean
        If IsNumeric(stringNumber) Then
            If CDbl(stringNumber) = CDbl(Int(stringNumber)) And CInt(stringNumber) >= 0 Then
                Return True
            End If
        End If
        Return False
    End Function

    'Name:         FindPrimeFactors
    'Parameters:   inNumber - integer to find its prime factors, MUST BE POSITIVE
    'Returns:      String of inNumbers prime factors, separated by spaces
    'Description:  Finds the parameters prime factors and returns them as a string, each
    '              factor separated by a space
    Function FindPrimeFactors(ByVal inNumber As Integer) As String
        Dim factors As String = "", currentFactor As Integer = 2
        'The prime factorization of 1 is 1
        If inNumber = 1 Then
            factors &= "1 "
        Else
            'Loop while there are still factors left
            Do While inNumber > 1
                'If the current number can be divided by the current factor 
                If inNumber Mod currentFactor = 0 Then
                    'Add the current factor to the string and divide the current number by the
                    'current factor
                    factors &= CStr(currentFactor & " ")
                    inNumber = inNumber \ currentFactor
                Else
                    'Increment the current factor
                    currentFactor += 1
                End If
            Loop
        End If
        'Return the list of factors
        Return factors
    End Function
End Class