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How to Calculate

Hi i want make a calculator, using visual basic 6.0
> 2 textboxes and 1 command button
in first textbox input will be like this  180.25*10-26+400/2  (etc...)
and answer will be on second text box on command button Clicked

How can i do this
please assist me

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crystal_Tech
Asked:
crystal_Tech
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1 Solution
 
Mike TomlinsonMiddle School Assistant TeacherCommented:
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crystal_TechAuthor Commented:
Thanks for reply
But its giving me error
compile error : user defined type not defined
and highlighted on
ScriptEngine As New MSScriptControl.ScriptControlClass



Private Sub Command1_Click()
      Dim ScriptEngine As New MSScriptControl.ScriptControlClass
        ScriptEngine.Language = "VBScript"
        Dim problem As String
        problem = Text1.Text
        Dim answer As String
        answer = ScriptEngine.Eval(problem)
        MessageBox.Show (answer)
End Sub
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Mike TomlinsonMiddle School Assistant TeacherCommented:
Right...as stated in the linked answer, you need to add a REFERENCE to the Microsoft Script Control 1.0.
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crystal_TechAuthor Commented:

Sir
I already added
Microsoft Script Control 1.0.

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Mike TomlinsonMiddle School Assistant TeacherCommented:
*Haven't code in VB6 in literally years...

Try it like this:

    Dim ScriptEngine As New ScriptControl

Or maybe:

    Dim ScriptEngine As ScriptControl
    Set ScriptEngine = New ScriptControl
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crystal_TechAuthor Commented:
Compile Error
Invalid use of new keyword

Highlighted on ScriptEngine As New ScriptControl

and when i am using

Dim ScriptEngine As ScriptControl
    Set ScriptEngine = New ScriptControl

Highlighted on  New ScriptControl

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Mike TomlinsonMiddle School Assistant TeacherCommented:
You could just add the Script Control directly to your form like any other control:
http://support.microsoft.com/kb/184740
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crystal_TechAuthor Commented:
sir

Getting Run Time Error '424'
Object Required
and on debug highlighted to             ScriptEngine.Language = "VBScript"

Using following code

        With ScriptControl1

            ScriptEngine.Language = "VBScript"
            Dim problem As String
            problem = Text1.Text
            Dim answer As String
            answer = ScriptEngine.Eval(problem)
            MessageBox.Show (answer)
        End With

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Mike TomlinsonMiddle School Assistant TeacherCommented:
"With ScriptControl1"

Your control is called ScriptControl1.

...so change all "ScriptEngine" to "ScriptControl1".
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crystal_TechAuthor Commented:

Getting Wrong Answer

Private Sub Command1_Click()
Text2.Text = ""
        With ScriptControl1

            ScriptControl1.Language = "VBScript"
            Dim problem As String
            problem = Text1.Text
            Dim answer As String
            answer = ScriptControl1.Eval(problem)
            Text2.Text = answer
        End With
End Sub

input is in text one
150+150+150*3-100
and aswer should be 1250 instead of 650

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Mike TomlinsonMiddle School Assistant TeacherCommented:
How are you getting 1250?

That would be interpreted as:

    150+150+(150*3)-100
    150+150+450-100
    650

In the absence of parenthesis, Multiplication/Division is always calculated before Addition/Subtraction.
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crystal_TechAuthor Commented:

oh ok but sir
i want it like that
150+150+150*3-100 = 1250
instead of 650
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Mike TomlinsonMiddle School Assistant TeacherCommented:
then you need to add parenthesis to force the addition to occur before the multiplication:

    (150+150+150)*3-100 = 1250
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Mike TomlinsonMiddle School Assistant TeacherCommented:
See:
http://msdn.microsoft.com/en-us/library/6s7zy3d1(VS.85).aspx

    "When multiplication and division occur together in an expression, each operation is evaluated as it occurs from left to right. When addition and subtraction occur together in an expression, each operation is evaluated in order of appearance from left to right. Parentheses can be used to override the order of precedence and force some parts of an expression to be evaluated before others. Operations within parentheses are always performed before those outside. Within parentheses, however, operator precedence is maintained."
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crystal_TechAuthor Commented:

Please show me sir how to do that

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Mike TomlinsonMiddle School Assistant TeacherCommented:
Are you kidding me?.... =\

Place this:

    (150+150+150)*3-100

into your Text1 control and see what the answer is.
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Mike TomlinsonMiddle School Assistant TeacherCommented:
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crystal_TechAuthor Commented:

No Sir I am Not kidding

your solution is absolutely correct
but my requirement is not 650 is 1250
so is there any way to remove operator ( ) and calculate complete line
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crystal_TechAuthor Commented:
i am gonna use only 4 following operators

+  -  *  /


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mlmccCommented:
How do you know the answer is 1250?

mlmcc
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Mike TomlinsonMiddle School Assistant TeacherCommented:
If you want to use a custom precedence for operators (without parenthesis) then you can't use the Script Control.

You'd either have to use a different canned control or write your own lexical parser from scratch.

Can you give more details about how this is going to be used?
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Mike TomlinsonMiddle School Assistant TeacherCommented:
For your limited set of operators, and left to right evaluation WITHOUT precedence:
http://www.devx.com/vb2themax/Tip/18651
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crystal_TechAuthor Commented:

Sir Thats it
Word to word

A simple expression evaluator by Francesco Balena

Thank you So much Sir

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