Mathematical Language Evolution Design
Introduction
This document describes the modifications that occur to the Event-B mathematical language from the developer point of view. The old language will still be recognized, in order to provide backward compatibility.
Syntax Tree
Deprecated nodes (becoming atomic expressions):
- KPRJ1
- KPRJ2
- KID
New nodes:
- KPARTITION that represents the new partition predicate (relational predicate)
- KPRJ1_GEN that represents the atomic version of the first projection
- KPRJ2_GEN that represents the atomic version of the second projection
- KID_GEN that represents the atomic version of the identity
Parser Changes
The new parser has a version attribute. Depending on the version, formulas are parsed differently. Thus, the KPARTITION node is illegal if version is V1. It is accepted only from version V2. Concerning, identity and projections, they are recognized as non-generic with V1 and generic with V2. The following table summarizes how tokens are processed depending on the parser version:
| Parser V1 | Parser V2 | |
|---|---|---|
| "partition" | illegal | KPARTITION |
| "id" | KID | KID_GEN |
| "prj1" | KPRJ1 | KPRJ1_GEN |
| "prj2" | KPRJ2 | KPRJ2_GEN |
Parsing
FormulaFactory has new parse() methods with a parser version argument. Existing methods default to the latest version. To cope with version problems, parsing is done in several steps:
- try to parse with the given version (or latest by default)
- if parse succeeds, the result is returned as usual
- else, try to parse with older versions incrementally
- if no version succeeds, return the failed result of the parse call with the latest version
- else propose upgrading from the highest succeeding version to the latest
Multiple Predicates / Partition
A new predicate class is introduced: MultiplePredicate that is abstract and superclasses Partition. A MultiplePredicate is a predicate that applies to a list of two or more expressions. In a Partition, all expressions must have the same type, that is the type of the partitioned set (first child).
Visitors
IVisitor has three more methods:
- enter KPARTITION
- continue KPARTITION
- exitKPARTITION
ISimpleVisitor has one more method:
- visitMultiplePredicate
Sequent Prover
TODO
Affected client code
TODO
