CS 541 Lecture -*- Outline -*-

* Structural operational semantics of BeCecil

	work out the semantics of BeCecil in class.

** overview

*** what has to be done
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     WHAT HAS TO BE DONE TO WRITE
       A SEMANTICS FOR BECECIL?

Tasks:
   (informal understanding)
   concrete syntax
   (examples, informal explanations)
   abstract syntax
   big step or little step?
   data structures (domains)
   rules for each piece of syntax

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        or any language

*** abstract syntax

        Q: Do we want recursive declaration sequences as a type?
        Q: What about class names?

        considerations: ease of writing programs, clarity,
                        correspondence to the defining document.

*** semantic domains
**** objects
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            OBJECTS

module object.

import inherits set.

% kind objectId = int.
kind object type.


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        Q: How do we make objects?  How to program oid?

...     type mkObject int -> finite_rel int int
              -> set case -> set case -> object.
        type oid -> object -> int -> o.
        oid (mkObject ID I IS AS) ID.

**** inheritance relationships
        Q: Why are inheritance relationships represented as things in BeCecil?

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        INHERITANCE RELATIONSHIPS

module inherits.

import finite_rel.

type leq_inh finite_rel int int
             -> int -> int -> o.

leq_inh I ID1 ID2 :- related I ID1 ID2.
leq_inh I ID ID.

((leq_inh I ID1 ID2), (leq_inh I ID2 ID3))
=> %-------------------------------------
         (leq_inh I ID1 ID3).
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        Q: Will this cause computational problems for us?
        Q: Can you write a \Prolog rule for ancestors membership (figure A-4)?

**** generic functions
        discuss the broad outlines, and then closures, storage tables,
                and assignments
        case sets, applicability

**** contexts, environments, elaborateds

        explain the distinctions and how they work

**** stores

        similar to environments.  How about allocation?

*** rules
        describe how to code some in \Prolog

        start at the end (actual arguments, expressions, ...) and work back.

        Q: How would you write a little step semantics for BeCecil?