Roman Numeral Calculator

[xtishx]

Hey I'm doing coursework in VB 6 and the task is to:

• allow a user to enter numbers in Roman numerals, according to the additive rule, each up to a maximum value of 4000 (MMMM)
• prevent the user entering an invalid Roman numeral
• display the numbers entered in both Roman numerals and their Arabic decimal equivalent
• allow the user to enter an operator for addition or subtraction
• prevent the result of a subtraction being zero or a negative number
• display the result of the calculation in both Roman and Arabic decimal forms
• allow the user to clear all displays

The additive rule in this case is to make sure that you enter numerals in descending order of value and a letter may not be repeated if it can be replaced (e.g. IIIII can be replaced with V). In this question 4 is classed as being IIII and NOT IV.

I've created an inteface that allows the user to enter an already valid Roman numeral (i.e. not validated by the program itself), it displays the numbers and answers in both numeral and decimal forms, the user can add or subtract the numerals and there is an option to clear all displays.

But I'm having problems trying to write the validation rules for:

• making sure the numeral that is entered is in the correct order
• the additive rule (explained above)

If anyone can help it would be much appreciated! Thanks!

xtishx

[mebhas]

well, i didnt go thru all your specifications but what u need to do is do a code check in the change event. what i mean basically is to check what has been entered into a textbox everytime something is typed in.

[Andrew G]

Sorry it took so long to reply, but tada . Btw Welcome to the forums

For this you'll need one textbox and one label

Const RomanNumerals As String = "IVXLCDM"
Dim MaskedString As String
Dim NumUsed(0 To 7) As Long
 
Private Sub Form_Load()
MaskedString = String(7 * 4, "#")
End Sub
 
Private Sub Text1_KeyPress(KeyAscii As Integer)
 
pos = InStr(1, RomanNumerals, UCase(Chr(KeyAscii)))
If pos And NumUsed(pos) < 4 Then
    strpart = Mid(MaskedString, (pos * 4) - 3, 4)
    strpart = Replace(strpart, "#", UCase(Chr(KeyAscii)), , 1)
    If UCase(Chr(KeyAscii)) = "I" Then
        MaskedString = strpart & Mid(MaskedString, (pos * 4) + 1)
    Else
        MaskedString = Mid(MaskedString, 1, (pos * 4) - 4) & strpart & Mid(MaskedString, pos * 4 + 1)
    End If
   
    NumUsed(pos) = NumUsed(pos) + 1
    KeyAscii = 0
ElseIf KeyAscii = 8 And Text1.SelStart > 0 Then
    Letter = Mid(Text1.Text, Text1.SelStart, 1)
    pos = InStr(1, RomanNumerals, UCase(Letter))
    If NumUsed(pos) > 0 Then NumUsed(pos) = NumUsed(pos) - 1
    
    strpart = Mid(MaskedString, (pos * 4) - 3, 4)
    strpart = Replace(strpart, Letter, "#", , 1)
    If Letter = "I" Then
        MaskedString = strpart & Mid(MaskedString, pos * 4 + 1)
    Else
        MaskedString = Mid(MaskedString, 1, (pos * 4) - 4) & strpart & Mid(MaskedString, pos * 4 + 1)
    End If
    
Else
    KeyAscii = 0
End If
 
    Text1.Text = Replace(MaskedString, "#", "")
    Label1.Caption = (NumUsed(1) * 1) + (NumUsed(2) * 5) + (NumUsed(3) * 10) + _
                     (NumUsed(4) * 50) + (NumUsed(5) * 100) + (NumUsed(6) * 500) + _
                     (NumUsed(7) * 1000)
End Sub

[the emily]

hello, im doing the same course as xtishx
we tried your code Andrew G (thanks by the way) and there is just one small problem, the roman numeral is in the opposite order to what is required. I cant seem to the solution to this problem myself. I think only a simple alteration is needed though id be grateful if somebody would tell us what!
Thanks again

the emily

[Andrew G]

simply reverse the order in

Const RomanNumerals As String = "IVXLCDM"

to

Const RomanNumerals As String = "MDCLXVI"

[xtishx]

Hey

I tried reversing the string and now it comes up with the wrong decimal equivalents, i.e. I now equals 1000 and M equals 1...so what do we have to change in the rest of it so that it comes up with the right decimal equivalent?

[Andrew G]

Oops

Const RomanNumerals As String = "MDCLXVI"
Dim MaskedString As String
Dim NumUsed(0 To 7) As Long
 
Private Sub Form_Load()
MaskedString = String(7 * 4, "#")
End Sub
 
Private Sub Text1_KeyPress(KeyAscii As Integer)
 
pos = InStr(1, RomanNumerals, UCase(Chr(KeyAscii)))
If pos And NumUsed(pos) < 4 Then
    strpart = Mid(MaskedString, (pos * 4) - 3, 4)
    strpart = Replace(strpart, "#", UCase(Chr(KeyAscii)), , 1)
    If UCase(Chr(KeyAscii)) = Left(RomanNumerals, 1) Then
        MaskedString = strpart & Mid(MaskedString, (pos * 4) + 1)
    Else
        MaskedString = Mid(MaskedString, 1, (pos * 4) - 4) & strpart & Mid(MaskedString, pos * 4 + 1)
    End If
   
    NumUsed(pos) = NumUsed(pos) + 1
    KeyAscii = 0
ElseIf KeyAscii = 8 And Text1.SelStart > 0 Then
    Letter = Mid(Text1.Text, Text1.SelStart, 1)
    pos = InStr(1, RomanNumerals, UCase(Letter))
    If NumUsed(pos) > 0 Then NumUsed(pos) = NumUsed(pos) - 1
    
    strpart = Mid(MaskedString, (pos * 4) - 3, 4)
    strpart = Replace(strpart, Letter, "#", , 1)
    If Letter = Left(RomanNumerals, 1) Then
        MaskedString = strpart & Mid(MaskedString, pos * 4 + 1)
    Else
        MaskedString = Mid(MaskedString, 1, (pos * 4) - 4) & strpart & Mid(MaskedString, pos * 4 + 1)
    End If
    
Else
    KeyAscii = 0
End If
 
    Text1.Text = Replace(MaskedString, "#", "")
    Label1.Caption = (NumUsed(1) * 1000) + (NumUsed(2) * 500) + (NumUsed(3) * 100) + _
                     (NumUsed(4) * 50) + (NumUsed(5) * 10) + (NumUsed(6) * 5) + _
                     (NumUsed(7) * 1)
End Sub

[BruceG]

I have sample code on my site that may assist you.
On this page:
http://www.thevbprogrammer.com/tutorials.html
Under "8. Control Basics", see the Programming Exercise for Roman Numerals.

[superleeds27]

Im also doing this course!

Man its hard!

Im still in design stage, i dont ven knoe how to use Visual Basic, Ill prolly fail this course, got U in ma test!

Anyways can any of you who have done it help me out a little, like code where?

or maybe send me it , lol

Just this is so confusing, and my teacher doesn't even help me, i dont think he likes me!

[leinad31]

Here's a solution... hopefully the correct one, not a MMMM or IIII or XXXX solution. I don't have VB here so I can't test... this is all theoretical.

Translate the character string into an addition formula. Replace the "left char less than right char" combinations first using string manipulation, eg Replace() function. Then replace the rest with their proper equivalents.

CMLXXIV --> 900 + LXX + 4 --> 900 + 50 + 10 + 10 + 4

locate and replace CM with 900...
replace CD with 400...
replace XC with 90...
replace XL = 40...
replace IX = 9...
replace IV = 4...

Validity check for the previously mentioned replacements, the respective character should not appear again. Example for a CM replacement there should be no other C's, IV no other I's, etc.

Insert here a character count check... there should be no more than 3 instances of selected characters such as X. Other characters such as V, there should only be one instance.

continue with replacements of remaining roman characters
replace M = 1000...
replace D = 500...
reaplce C = 100...
and so on and so forth

An additional check that the original roman numeral was valid, the decimal values should be decrementing (in some cases equal, but not in the other direction). If you check the previous equation, you will notice that 900 > 50 > 10 >= 10 > 4. This step might not be necessary, I can't say for certain right now.

Lastly to get the decimal equivalent of the euqation there's a special function (or control??) to equate that. I forgot the name of the function and the project reference necessary. Ask around for that function... the function that gets the math result of a string equation.

There are minor details, depending on how you use the replace function... such as a trailing operand in which case you'll have to add zero to get a valid equation. I'll let you figure out the minor details.

[superleeds27]

doesn't help me

[leinad31]

Programming is not solely coding... there's also analysis involved.

In real life, don't expect your boss or systems analyst to give you source code. You will have to learn to understand a narrative explanation (often not written) given to you by a systems analyst. Your job then is to implement the program as specified by the requirements and the design/flow indicated by the analyst then do some debugging..

[superleeds27]

i still carnt do it! baffled beyond belief

[leinad31]

Read up on the Replace() function, the Microsoft Script Control and the Eval() method of the script control.

Make your own source code implementation and post that here, we can then continue the discussion based on your implementation.

[DKenny]

Have a look at my post here.

[superleeds27]

DKenney!

What does that code do?

[DKenny]

As stated in the commets for the function

This function returns a string that is the Roman Numeral version of a passed Arabic number. The function will only work if the value is less than 4000.

[superleeds27]

Ok, ya see i dunt understand im not VB NERD!

lol, just need a this calculator doing!

[RhinoBull]

You may also check out Converting Numbers to Roman Numerals (and Back) sample written by Randy Birch.

[superleeds27]

anyone help me more then giving me code, and weird informtion!?

[leinad31]

But I'm having problems trying to write the validation rules for:

• making sure the numeral that is entered is in the correct order
• the additive rule (explained above)

My previous post was hasty so...

As with any string manipulation routine, you will have to prepare your string to facilitate manipulation, eg. no spaces, UCase(), and so on. Use the validate event of the textbox. I used only one textbox in my tests.

You will then have to parse the roman expression and place it in a structure to facilitate iteration through the operands and operators. I found inserting vbCrLf works.

Public Sub ExpressionToArray(ByVal Expression As String, RetArray() As String) As Long 
   ExpressionToArray = -1  'init value
 
   'It is assumed that spaces have already been eliminated
   Expression = Replace(Expression, "+", vbCrLf & "+" & vbCrLf)
   Expression = Replace(Expression, "-", vbCrLf & "-" & vbCrLf)
   Expression = Replace(Expression, "*", vbCrLf & "*" & vbCrLf)
   Expression = Replace(Expression, "/", vbCrLf & "/" & vbCrLf)
 
   'You can insert a check here
   'If there is a leading or trailing vbCrLf, or there are two consecutive vbCrLf's 
   '   in the expression then you are lacking operands or have to many operators
 
   RetArray = Split(Expression, vbCrLf)
   ExpressionToArray = 0
End Sub
 
'You can then iterate on the returned array, eg:
'
'Dim sArray() As String
'
'   Call ExpressionToArray(txtInput.Text, sArray)
'   For x=0 To Ubound(sArray)
'      Select Case sArray(x)
'      Case "+", "-", "*", "/"
'         'do nothing, skip operators
'      Case Else
'         Call RomanToDecimal(sArray(x))  'pass the roman operand and update array value
'      End Select
'   Next
'
'   txtOutput.Text = EvaluateExpression(Join(sArray, ""))

You can then do 3 levels of validation on each roman operand:
- An initial check to screen out invalid characters (A, B, E...) and the more obvious errors such as IL or VV. This can easily be accomplished with InStr() > 0

- Validity checks during the conversion into an expression based on places (thousands, hundreds, tens, and ones as mentioned in Rhino's link).

- Rechecking the expression to make sure that the values progress from thousands place to ones correctly as I explained in an earlier post.

Conversion based on digit place is a lot easier than nested conditional statements to process the string from left to right. You will also need a sub to count the number of instances of your roman character.

Public Function CharCount(RomanChar As String, Expression As String) As Long
Dim sTemp As String
 
   sTemp = Replace(Expression, RomanChar, "")
   CharCount = (Len(Expression) - Len(sTemp)) / Len(RomanChar)
End Function
 
Public Function RomanToDecimal(ByRef RomanNum As String) As Long
'note that I passed by reference so I can update the value of RomanNum in the called procedure
 
   RomanToDecimal = -1
 
   If SimpleCheck(RomanNum)  <> ) Then error occured 'check for common errors and invalid letters
   If ReplaceOnes(RomanNum) <> 0 Then error occured 
   If ReplaceTens(RomanNum) <> 0 Then error occured
   If ReplaceHundreds(RomanNum) <> 0 Then error occured
   If ReplaceThousands(RomanNum) <> 0 Then error occured
   'you will need to correct the leading + sign in the final expression
 
   If PlacesCheck(RomanNum) <> 0 Then error occured
   'You will reuse ExpressionToArray() in placescheck() to 
   'get an array to check by iteration to ensure that
   'the decimal values progress in order from thousands to ones
 
   romanNum = EvaluateExpression(RomanNum) & ""
 
   RomanToDecimal = 0  'completed successfully
End Function
 
 
'Pseudocode for ones place, do the same for the other places
' note validity checks during conversion
Public Function ReplaceOnes(ByRef Expression As String) As Long
Dim IVcount As Long
Dim IXcount As Long
 
   ReplaceOnes = -1
   IVcount = CharCount("IV", Expression)
   IXcount = CharCount("IX", Expression)
 
   If IVcount > 0 and IXcount > 0 Then
      'error, IX and IV cannot exist at the same time    
   ElseIf IVcount > 1 Then
      'error, only one IV in a number
   ElseIf IXcount > 1
      'error only one instance of IX is valid
   ElseIf IVcount = 1  
      'notice no need to check IXcount = 0, 
      'it is implied cause first case already handles IVcount > 0 and IXcount > 0
      Expression = Replace(Expression, "IV", "+4")
      If CharCount("I", Expression) > 0 Or CharCount("V", Expression) > 0 Then
         'error, I's or V exist when IV already used
      End If 
   ElseIf IXcount = 1
      'almost same format as IVcount = 1, test I's and X
   ElseIf IVcount = 0 and IXcount = 0
      If CharCount("V", Expression) > 1 Then
         'error, only one V is valid
      Else
         Expression = Replace(Expression, "V", "+5")
      End If
 
      If CharCount("I", Expression) > 3 Then
         'error, only up to 3 I's valid
      Else
         Expression = Replace(Expression, "I", "+1")
      End If
   End If
 
   ReplaceOnes = 0 'completed with no errors
End Sub
 
Public Function EvaluateExporession()
Dim oSCRCNT As New ScriptControl
 
   'sorry have to go... but this will have only about 3 to 5 lines
   'anyone for the save??
End Function

And I mentioned the script control and the eval method. Thread starter, this is what you will use to perform arithmetic operations on your roman numerals.

You enter an expression: "X + VII"
You get an expression array and call romantodecimal:
Array("10","+","5 + 1 + 1") --> Array("10","+", "7") after romantodecimal call
RomanToDecimal also performs the Eval method of the script control to get the result of 5+1+1 = 7
You then perform another Eval on the final expression "10+7"

You will need to set the project reference of the script control
You will need to create a new instance of the object in EvaluateExpression()
you will need to set the lagnuage property of the object to "vbscript"
Then finally call the Eval method and get the result of your arithmetic expression.

[savara]

This should be useful.

This is AS level Computing Coursework. The Course specifically states:

The work which you submit for assessment must be your own.

If you copy from someone else or allow another candidate to copy from you, or if you cheat in
any other way, you may be disqualified from at least the subject concerned.

I am in the same boat as you, I had to to (and have already finished) this same coursework; go ask the one person you're allowed to: your teacher.

[superleeds27]

Still confused,

Thanks for all your help with it,

I have code, just need to assign the code to a button, if ya get wot i mena

[litlewiki]

I have sample code on my site that may assist you.
On this page:
http://www.thevbprogrammer.com/tutorials.html
Under "8. Control Basics", see the Programming Exercise for Roman Numerals.

hey bruce any concessions for vbforums members.why dont u send me a copy of that ebook free of cost

[superleeds27]

im still no further on with it

[Hack]

im still no further on with it

What is the current stumbling block?

[superleeds27]

well, i have my design and the boxes labelled

I just have no idea what to do in Vb, no idea of code or anything

[Hack]

well, i have my design and the boxes labelled

I just have no idea what to do in Vb, no idea of code or anything

No code

There is a whole thread full of code here.

[superleeds27]

yer no idea where to put it, or anything, totally new to VB

[jude7]

@superleeds27 : try to ask xtishx (Thread Starter) if both of u are taking the same course. Ask him/her, how to start VB, design the form and how to put the code. Then try to read this thread form the begining. Becouse we don't know in which level of VB's Programmer u are.

- jude7 -

NB: Have u done a "Hello World" project ?

[leinad31]

Superleeds,

If what your doing is based on my code then in the code I posted, the one place in the command button's click event is...
BTW, Its in pseudocode

'You can then iterate on the returned array, eg:
'
'Dim sArray() As String
'
'   Call ExpressionToArray(txtInput.Text, sArray)
'   For x=0 To Ubound(sArray)
'      Select Case sArray(x)
'      Case "+", "-", "*", "/"
'         'do nothing, skip operators
'      Case Else
'         Call RomanToDecimal(sArray(x))  'pass the roman operand and update array value
'      End Select
'   Next
'
'   txtOutput.Text = EvaluateExpression(Join(sArray, ""))

Note:

1) The textbox.text value is parsed (string manipulation) with ExpressionToArray() to isolate the operands (or the roman numerals as strings) as a member of an array

2) You then iterate through the array/operands (skipping the operators) and replacing each roman numeral string with its equivalent decimal value.

3) The modified array (decimal operands) is then converted into a single string expression through Join()

4) This 'concatenated' expression is then passed to the Eval method of the script control and the result (a decimal) is shown in another textbox.


I used the script control approach due to the thread starters other requirements as I quoted in my previous post. Code I left out are SimpleCheck(), PlacesCheck() and the convertion for the tens, hundreds and thousands place. I had assumed the thread starter could build up on the concept and do the other code himself.