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Equality in E |
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A surprising number of seemingly separate issues in the design of E all come together in the definition of the equality operations -- security, the reference taxonomy, partial order constraints, the object-passing taxonomy, and the collection classes. E has two equality operations, the predicate same and the function join.
- In the E language, one tests if two references, x and y, are the same with "x == y". The Java/ELib programmer instead says "E.same(x, y)". Both are spoken as "Is x the same as y?".
- In the E language, one forms the join of x and y with " def z := E.join(x, y)", which is spoken as "z is a vow for the join of x and y."
This Chapter uses the notation of the E language, but the Java/ELib programmer should find everything easy to translate.
| The Grant Matcher Puzzle | Defines the security problem E's equality operations need to solve. |
| 4-Party Partial Orders | Defines the concurrency problem E's equality operators need to solve. |
| Object Sameness | When are two objects the same? |
| Reference Sameness | When are two references the same? Reference sameness and object sameness are mutually recursive definitions, but the base cases are mostly in object sameness, which should therefore be read first. |
| Argument Passing Rules | When a reference of a given kind is passed by an invoation of a given kind, what kind of reference is received? |
| Joining References | Eventual mutual acceptability |
Unless stated otherwise, all text on this page which is either unattributed or by Mark S. Miller is hereby placed in the public domain.
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