How should I name output variables that are the same as the function?

Question

What are some conventions for naming a variable in cases where the name of the variable ought to be identical to the name of the function? I'm using VB.Net.

I often have this problem when writing functions that either perform some mathematical operation, or generate an object. The return variable is declared inside the function, and values in that variable are set throughout the function.

As an example:

Public Function Sum(arrayOfValues as double()) as double()
   dim outputSum as double(arrayOfValues.GetUpperBound(0))
   For i As Integer = 0 To arrayOfValues .GetUpperBound(0)
            outputSum += v(i)
        Next
   Return outputSum 
End Function

Here outputSum could not be simply called "sum". Since VB.Net is case insensitive, the name would conflict with the name of the method.

Here's another example:

    Public Function IsValid(data As List(Of MyObj)) As Boolean
        Dim retVal As Boolean = True
        For Each d As MyObj In data
            If d.SomeProperty > 42 Then
                retVal = False
            End If
        Next
        Return retVal
    End Function

What name can I use that is clear, but does not add unnecessary noise? In the past I have used just "output", and sometimes "retVal" if the return type is of primitive type.

*I've also seen many coders use arbitrary abbreviations just to get around the compiler (such as "MaximumValue" and "maxVal"). This drives me crazy.

Answer 1

Most frequently, I use the variable result.

Don't create ambiguity in the mind of the next Gentle Reader of your source-code. (Since, too bad for you, you just got smooshed by a bread truck, she can't ask you to clarify.) Try to write source code that is "clear 'at a glance.'" Because sometimes the peoople who will be reading it are in a hurry and under pressure. Try to be nice to them ...

Answer 2

VB is a special child among the .NET family in that it is case insensitive (maddeningly so). So I've felt this pain before.

First of all, a good rule of thumb is to have your methods be named after Verbs and your variables/objects be named after Nouns, that often times resolves the conflict.

However if that isn't the case, then I'd use a combo of underscore and lowercase for your result object inside the method:

Public Function Sum(arrayOfValues As Double()) As Double()
    Dim _sum As Double(arrayOfValues.GetUpperBound(0))
    For i As Integer = 0 To arrayOfValues.GetUpperBound(0)
        _sum += v(i)
    Next
    Return _sum
End Function

Answer 3

You could sensibly go at this two ways.

One is to use a consistent prefix, like 'ret' or 'out' - so calling the variable 'out_sum'. I also apply this naming system to out parameters.

The other is to name the variable in question something different - like 'accumulator', or maybe abbreviated to 'cuml_sum' - which is more appropriate to its role as an intermediate variable used in the calculation process.

A possible third alternative - which is available in VB6 and VBA (because of how those languages actually assign return values), but I forget now whether it was carried forward to VB.Net - is to use the function name itself as the accumulator variable.