controller.operations library Null safety

The calculator operations. This is split into its own library so that it's encapsulated from the controller internals. Operations are split into various types, viz:





Note the contravariant relationship between operation types and major state typess. This is discussed in more detail in the controller.states library description.

Classes

Operations
The calculator operations. This is split into its own library so that it's encapsulated from the controller internals. This class is just a collecting place for the static final Operation constants, and some lists of operations that are useful. [...]