Android Question Convert String to Operator

JohnD · Jul 31, 2014

I am trying to convert the string "*" to the multiplication operator for an on the fly creation of a calculation. Below are the the stabs in the dark I have tried and their respective error messages reported by the compiler.

In all cases assume: Dim sMult = "*" as String

B4X:

'1
iAns = (iNum1) &sMult (iNum2)
'2
iAns = iNum1 &sMult iNum2
'3
iAns = iNum1 "\sMult" iNum2

Error 1
Parsing code. Error
Error parsing program.
Error description: Use of undeclared array: smult
Occurred on line: 34
iAns = (iNum1) &sMult (iNum2)

Error 2
Parsing code. Error
Error parsing program.
Error description: Syntax error.
Occurred on line: 34
iAns = iNum1 &sMult iNum2

Error 3
Parsing code. Error
Error parsing program.
Error description: Syntax error.
Occurred on line: 35
iAns = iNum1 "\sMult" iNum2

Any help on this would be greatly appreciated. Thanks, JD

klaus · Jul 31, 2014

You can't convert a string or character to an operator.
You would need something like this:

B4X:

Select sMult
Case "+"
    iAns = iNum1 + iNum2
Case "-"
    iAns = iNum1 - iNum2
Case "*"
    iAns = iNum1 * iNum2
Case "/"
    If Abs(iNum) > 1E-15 Then
        iAns = iNum1 / iNum2
    Else
        ToastMessage("Error: Zero devider", False)
    End If
End Select

Mark Read · Jul 31, 2014

Not clear whar you are doing here, is iAns a string? Num1 & 2 I assume are values not string.
Do you want to build a string like: "4 × 5 = 20"? Pls explain a little better.

Mark Read · Jul 31, 2014

Ok Klaus was quicker!

JohnD · Jul 31, 2014

@klaus - What I expected and what I'm currently doing. But I figured it wouldn't hurt to ask. My ultimate implementation is to store user-defined calculations in a db. My plan is to store variables in one db field and operators in another - possibly comma-demimited in their respective fields for readability. Populate arrays from each field and pass the incremental calculations through case statements. It would have been nice to eliminate the case statements though.

Oh, thanks for the reply and the phantom-decimal digits logic for division.

klaus · Jul 31, 2014

Maybe the Expression Evaluator could be of interst for you.

JohnD · Jul 31, 2014

I will check it out. Thanks!

Android Question Convert String to Operator

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