An Assertion Language

A possible assertion language
- Logical expressions - as in the programming language
- Programmed assertions - via boolean functions of the programming language
  - Should be simple functions
  - Problems if there are errors in these
- Universal ("for all...") and existential ("there exists...") quantifiers
  - Requires programming - iteration - traversal
  - It may be expensive to check assertions with quantifiers
- Informal assertions, written in natural language
  - Cannot be checked
  - Much better than nothing
- Special means of expression
  - old Expr - The value of the expression at the beginning of the operation
  - nochange - A simple way to state that the operation has not changed the state of the object