order of operations "-" vs "[..]" (was: "Cannot negate ListValue")

[akrasuski1]

The following code:

SET test TO list().
test:add(1).
PRINT -test[0].

Should probably print -1. Instead, I get "Cannot negate ListValue".
In the beginning I thought it is because kOS doesn't know what is the type of the object in the list (string couldn't be negated surely), but the very same code works if I switch from negating to multiplying by -1.

[Dunbaratu]

This could merely be a simple matter of the order operations between the '[ ]' operator and the '-' operator.

Does this work?
PRINT - ( test[0] ).

It sounds like it's trying to do this: (-test) first and then do the [ operator.

The unary negation operator is a pain, when it comes to order of operations because it has different levels of precedence depending on context.

You want it to be very early when doing this:
-x + y
So it does that as (-x) + y instead of as -(x+y).

But you don't want it to be that early when doing other operations like [].

[akrasuski1]

Yes, you were right. Taking test[0] into brackets solves the issue. Perhaps the [] should have even bigger precedence? I don't think there's a situation when we want it the other way around: (-x)[15]. Either way, thanks for making it clear.

[Dunbaratu]

Changed the title so it is clearer in the list what the actual problem is that needs working on.