Changeset fbfd97bd for doc


Ignore:
Timestamp:
May 11, 2020, 12:35:36 PM (18 months ago)
Author:
Andrew Beach <ajbeach@…>
Branches:
arm-eh, jacob/cs343-translation, master, new-ast, new-ast-unique-expr
Children:
a7b486b
Parents:
0e7e3c17
Message:

Addition to the vtable proposal. We can recover the underlying type without a hierarchy.

File:
1 edited

Legend:

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  • doc/proposals/vtable.md

    r0e7e3c17 rfbfd97bd  
    237237default is provided or not, the second syntax can be used to pick a
    238238parameter on instantiation.
     239
     240### Extension: Object Access
     241This requires that the resolution scope (see below) is at the type level or
     242has explicate points with names. These are the tables and table names used
     243here.
     244
     245The system already knows where to find the virtual table and the object. If
     246the tables have particular identities, or on the user side names, then it is
     247meaningful to check if a binding virtual table is the same* as another. The
     248main use of this is virtual table declarations also give the type they bind
     249and if a binding table matches a known table then the underlyind object in the
     250trait object must be of that type.
     251
     252* By identity, by value would work and in some senses be more flexiable. But
     253  it would be slower and refering to further away functions would be harder.
     254
     255This gives one of the main new features of the hierarchical use of virtual
     256tables (see below); the ability to recover the underlying object. Or a pointer
     257of the approprate type it which both reflects the implementation and gives a
     258convenent way to encode the boolean/conditional aspect of the operation which
     259is that a different virtual table might be in use.
     260
     261There are two general ways to reperent this; a cast or a field access. The
     262cast is traditional and would definitely fit if a single pointer repersents
     263a trait object with the virtual table as part of the object. However for a
     264double pointer field access might be more approprate. By this system though
     265it is not the type that is used as the identifier but the virtual table. If
     266there is one table per type than it becomes equivilant again. Otherwise the
     267table has to be used as the identifier and the type is just a result of that
     268which seems important for syntax.
    239269
    240270Hierarchy
     
    560590be used in only some of the declarations.
    561591
    562     trait combiner fee = (summation_instance, sum);
     592    trait combiner fee = {summation_instance, sum};
    563593    trait combiner foe = summation_instance;
    564594
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