Empty stack error

Question

Hi everyone, I'm having trouble understanding an odd behavior in my small basic code.

So i would like to share 3 examples of code and ask why does the last one produces an error.

Case 1:

Stack.PushValue("a",1)
Stack.PushValue("a",2)
Stack.PushValue("a","result")

v1 = Stack.PopValue("a")
v2 = Stack.PopValue("a")
v3 = Stack.PopValue("a")

test[v3][v2] = v1

TextWindow.WriteLine(test[1][2]) ' -> "result". Works fine

Case 2:

Stack.PushValue("a",1)
Stack.PushValue("a","result")

test[Stack.PopValue("a")] = Stack.PopValue("a")
TextWindow.WriteLine(test[1]) ' -> "result". Works fine

Case 3:

Stack.PushValue("a",1)
Stack.PushValue("a",2)
Stack.PushValue("a","result")

test[Stack.PopValue("a")][Stack.PopValue("a")] = Stack.PopValue("a") ' -> Throws an error: Stack is empty
TextWindow.WriteLine(test[1][2])

Thanks,

Answer 1

It has something to do with the use of the Pop in an array index. See the output of:
Stack.PushValue("a",1)
Stack.PushValue("a",2)
Stack.PushValue("a",3)
Stack.PushValue("a","result")
TextWindow.WriteLine(Stack.GetCount("a"))
res = Stack.PopValue("a")
two=Stack.PopValue("a")
TextWindow.WriteLine(Stack.GetCount("a"))
test[Stack.PopValue("a")][two] = res
TextWindow.WriteLine(Stack.GetCount("a"))
TextWindow.WriteLine(test[1][2]) ' -> Prints nothing (empty)
TextWindow.WriteLine(test[1][3]) ' -> Prints "result" '
TextWindow.WriteLine(Stack.GetCount("a")) ' -> Prints 0. What happend to value 3 :)

Answer 2

It seems that the interpreter is working from right to left and the "=" is grabbing an element.

 case4:
    Stack.PushValue("n",1)
    Stack.PushValue("n",2)
    Stack.PushValue("n",3)
    Stack.PushValue("n",4)
    Stack.PushValue("n","result4")
    testn[Stack.PopValue("n")][Stack.PopValue("n")] = Stack.PopValue("n")     
    TextWindow.WriteLine(testn[2][3]) ' -> Prints "result" '
    TextWindow.WriteLine("Stackcount: " + Stack.GetCount("n")) 
    TextWindow.WriteLine("and the element is: " + Stack.PopValue("n")) ' ->
    TextWindow.WriteLine("Stackcount: " + Stack.GetCount("n")) ' -> 

Conclusion:
When writing to a multidimensional array and using at least one STACK.PopValue() in the index, the stack counter is erroneously decremented before use.