Re: Uninitialized "out" parameters

[fjh@mundook.cs.mu.OZ.AU (Fergus Henderson)]

dewar@cs.nyu.edu (Robert Dewar) writes:

>Dynamic bounds of arrays do not help in compile time legality checking, so
>I don't see what relevance they have. And yes, container types are certainly
>appropriate (after all see Bounded_String, which is exactly what you are
>talking about), but again, this has nothing to do with compile time legality
>requirements.

I think it does have relevant to the compile time legality
requirements.  Many container types have an interface that has no
possibility of accessing uninitialized variables even if their
implementation might make use of uninitialized arrays used in ways that
might make it difficult for a static checking system to ensure their
safety.  For example, if the standard library has a `sparse_hash_table'
type, it should solve the problem you mentioned with the 2 gig array.

The down side of strict static checking is that it might make some idioms,
such as an efficient implementation of the `sparse_hash_table' interface,
difficult to express.  The relevance of using containers with higher
levels of abstraction than arrays is that it allows you to combine
efficient implementations with strict static checking while minimizing
any loss of expressiveness.

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