VBScript summation

Question

I have this code that is trying to show the summation of;

All the even numbers from 0-100 or whatever number the user inputs

and then;

Show the summation of all the odd numbers from 0-100 or whatever number the user inputs.

Here is what I have so far:

Evennumber=InputBox("Please enter a even number!")

print "total + e"

For e= 2 to Evennumber step 2
  total= total+e
  print total&" +  "&e
Next

print total


Oddnumber=InputBox("Please enter a odd number!")
print "total + o"

For o= 1 to Oddnumber step 2
  total = total + o
  print total&" + "&o 
Next

print total

Is this correct?

user_5958455 · Answer

The key point is you didn't initialize total to zero before using it.

Option Explicit
Dim e, o, Evennumber, Oddnumber, total

Evennumber = InputBox("Please enter a even number!")

MsgBox "total + e"

total = 0
For e = 2 to Evennumber step 2
  total= total+e
  MsgBox total & " +  " & e
Next
MsgBox total

Oddnumber = InputBox("Please enter a odd number!")
MsgBox "total + o"

total = 0
For o = 1 to Oddnumber step 2
  total = total + o
  MsgBox total & " + " & o 
Next
MsgBox total

user_692942 · Answer

@iBug's answer is correct but it fails to point out key programming principles that you should try to follow that will benefit you in the long run. This example focuses on DRY (Don't Repeat Yourself) which if implemented would have made the re-set of total to zero a moot point.

Both processes of selecting a number and looping through the numbers by value are almost identical. When you have code like this, the best approach is to build a Function or Sub Procedure to handle the logic without requiring it to be duplicated.

Below we use a Sub Procedure called ProcessNumbers() and pass whether we want Even or Odd that way with a little initial setup we can use the same function to process both sets of numbers.

Option Explicit

'Even
Call ProcessNumbers(True)
'Odd
Call ProcessNumbers(False)

Sub ProcessNumbers(isEven)
  Dim i, startFrom, endAt, total, label
  Dim input, criteria

  If isEven Then 
    startFrom = 2
    endAt = 100
    label = "Even"
  Else
    startFrom = 1
    endAt = 100
    label = "Odd"
  End If
  input = InputBox("Please enter an " & label & " number!")
  If Len(input & "") > 0 And IsNumeric(input) Then endAt = CLng(input)
  For i = startFrom To endAt
    If isEven Then criteria = (i Mod 2 = 0) Else criteria = (i Mod 2 <> 0)
    If criteria Then
      total = total + i
      WScript.Echo total & " + " & i
    End If
  Next
  WScript.Echo total
End Sub

Output:

VBScript summation

2 Answers