[RESOLVED] Using variables to store equations

[Vinc3nt23]

Hi everyone, I have a question that i've tried my hardest to figure out (with- out and help) but I can't seem to get anywhere, here it is:

Lets say I declared "x" as it's own variable (single) and "y" as it's own variable (single), then I wanted to save the equation "y^(2+x)" in another variable - lets say "strEquation" (and I would guess string to be the most appropriate).

How could I solve the equation in "strEquation" if "x" was a value and "y" was a different value?

[crater]

post what you have so far?

[crater]

Private Sub Command1_Click()

Dim x As Double
Dim y As Double
Dim strEquation As Double
Dim answer As Double
x = Text1.Text
y = Text2.Text
strEquation = y ^ (2 + x)
answer = strEquation

Text3.Text = answer
End Sub

[Vinc3nt23]

none of my past attempts were any good, but to give you a better picture lets say:

I type "x+y^2" (or any other equation) into TextBox1 then when Command1 is pressed it displayed an answer in Label1 if "x" is a value I typed in TextBox2 and "y" was a value in TextBox3. How could I use any formula (with Xs and Ys in) typed in TextBox1 along with the values of x and y to give answer.
ie.

Dim y as Single
Dim x as Single
Dim strEquation as String

strEquation = TextBox1
y = TextBox3
x = TextBox2
Label1 = strEquation 'But this needs to be whatever the equation is...

[crater]

ok I think I see what you want to do:

1)You'll have to parse the string in text1
2) then use some conditional statements to convert x to what is in text2 and convert y to what is in text3. Hopefully text2.text & text3.text are integers
3) label1.caption = strEquation

Try looking into the Mid & InStr functions for the parsing

[rhahn]

We have strings of numbers that come in from OCR and then we use different math formulas against those numbers to see if they equal a check digit. One is add up all the numbers but the last two then mod 36 and that should equal the last two digits.
Every time we have a new formula we need to recompile the code. I have two ideas for fixing this but have not been able to test much.
First idea
Take the string that represents your formula and write it into tempFormula.vbs where this vbs returns the awnser. You could also use python or any other scripting language.
Second idea
form your formula into a select statement and send it to SQL then you'll get your answer as a record set.

Both require a fair amount of string parsing and the ability to convert your formula into the other language.

[CDRIVE]

You can't declare it as a String. How is VB going to perform math on a String?

[bushmobile]

Have a look at the Microsoft Script Control - you can give it a string equation and it will evaluate it:

Private Sub Command1_Click()
    MsgBox ScriptControl1.Eval("2^(1+2)")
End Sub

[Vinc3nt23]

Thank you all for the responses , and after reading through them I searched around abit on different websites about that scriptcontrol and found this:

TextBox1 has the equation
TextBox2 has teh value of X
label 6 is teh solution

Private Sub CommandButton1_Click()

FIn = TextBox1.Text
xVar = Val(TextBox2.Text)

FLenIn = Len(FIn)
Nx = 0

For i = 1 To FLenIn
If (Mid(FIn, i, 1) = "x" And Mid(FIn, i + 1, 1) <> "p") Then
Nx = Nx + 1
End If
Next i

FLenOut = FLenIn + 2 * Nx
Fout = ""

i = 0: j = 0
Do While j <= FLenOut
i = i + 1
j = j + 1
If (Mid(FIn, i, 1) = "x" And Mid(FIn, i + 1, 1) <> "p") Then
j = j + 2
Fout = Fout & xVar
Else
Fout = Fout & Mid(FIn, i, 1)
End If
Loop

Label5.Caption = Fout
Label6.Caption = Evaluate(Fout)


End Sub

it works (if I copy and paste some of the script for "y" as well), but I don't really understand exactly what it does, can anyone recommend a website that helps someone learn/improve their knowledge on in-depth VB6 scripting (or any scripting) like the dilemma I had?

[bushmobile]

As long as your formulas are always laid out in full (e.g. A * B + C rather than AB + C) then you can do something as simple as just using the replace function to put the values in the correct place:

Private Sub Command1_Click()
    Dim strFormula As String

    strFormula = Text1.Text ' e.g. "x+y^2"

    strFormula = Replace(strFormula, "x", Text2.Text)
    strFormula = Replace(strFormula, "y", Text3.Text)

    MsgBox ScriptingControl1.Eval(strFormula)
End Sub

[Vinc3nt23]

As long as your formulas are always laid out in full (e.g. A * B + C rather than AB + C) then you can do something as simple as just using the replace function to put the values in the correct place:

Private Sub Command1_Click()
    Dim strFormula As String

    strFormula = Text1.Text ' e.g. "x+y^2"

    strFormula = Replace(strFormula, "x", Text2.Text)
    strFormula = Replace(strFormula, "y", Text3.Text)

    MsgBox ScriptingControl1.Eval(strFormula)
End Sub

ty; this is very useful in the program i am trying to create

[MartinLiss]

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[CDRIVE]

Have a look at the Microsoft Script Control - you can give it a string equation and it will evaluate it:[code]Private Sub

This is good to know and admittedly I was unaware of it. That said, my reply was based on the OPs first post. In it he didn't mention that the formulas were in TextBoxes. The OP said he wanted to store his formulas in variables.

This is handy to know though. Thanks for posting it.

[todd.kauffman]

Not that this matters now, but you could simply create a function and pass in the X and Y value, run the equation and return the results.