As discussed in the first chapter, assignments in Tony are immutable. That means that once you declare a constant in Tony, you cannot re-declare its value.
Like in most other programming languages, constants are scoped to (i.e. accessible from) the block in which they are declared and all its children. Therefore, a constant declared within an abstraction is only available from within the same abstraction. On the other hand a constant declared outside an abstraction is available from within the abstractions that are created in the same block.
Lets look at an example. To globally define a