2.2. Pseudocode Notation
We use set notation in several places in this specification.
A (+) Bis the union of two sets, A and B.A (-) Bis the elements of set A that are not in set B.NULLis the empty set or list.
In addition, we use C-like syntax:
=denotes assignment of a variable.==denotes a comparison for equality.!=denotes a comparison for inequality.
Braces { and } are used for grouping.
Unless otherwise noted, operations specified by statements having multiple (+) and (-) operators should be evaluated from left to right, i.e., A (+) B (-) C is the set resulting from union of sets A and B minus elements in set C.