Question

I was quickly copying code from something else. Upon testing and debugging, I kept getting really strange results. After comparing the code again, I realized that I had added an extra = inside of my equation:

Dim lowerLeft As Integer = x = +y * terrainWidth

as opposed to this:

Dim lowerLeft As Integer = x + y * terrainWidth

What was this actually doing?

Answer 1

If you had Option Strict On (and you should), this wouldn’t compile.

A = inside an expression is a comparison operator. Its result is a Boolean. In your case, this means the expression is equivalent to:

Dim lowerLeft As Integer

If x = +y * terrainWidth Then
    lowerLeft = True ' Converted to 1
Else
    lowerLeft = False ' Converted to 0
End If

Option Strict On rightly forbids this implicit conversion.