Re: a new language, designed for safety !

["Randy Brukardt" <randy@rrsoftware.com>]

"Robert A Duff" <bobduff@shell01.TheWorld.com> wrote in message 
news:wccoaxss9po.fsf@shell01.TheWorld.com...
...
> For yet another example, it lacks the "tampering" business required by
> the RM.  I didn't need all sorts of Cursors pointing into the middle of
> Vectors, so I didn't need those run-time checks.

Reminder: Those run-time checks have two purposes: (1) to prevent iteration 
from going off into the weeds if the container is modified during iteration. 
Perhaps you only support iteration by indexes such that that isn't a 
problem. (2) to prevent elements from disappearing or causing erroneous 
execution while they are in use. There's nothing about "cursors pointing 
into the middle of vectors".

Indexing is only "safe" if some sort of element check is performed; in many 
cases the check isn't needed (if the element is used quickly and then 
discarded), but passing an element (or part of an element) as a parameter is 
common and there lie dragons.

The reason that using indexing in the standard containers is slow is because 
it requires compiler support to eliminate the check in the cases where it is 
not needed (probably over 90% of the cases in practice). But most 
implementors just write an Ada package and let the chips fall where they 
may. That won't give decent performance.

Other languages just let all container use be erroneous if one makes a 
mistake. We didn't want containers to be significantly less safe than an 
array (which doesn't have these issues as an element cannot be removed). 
Maybe that was a mistake, as safety no longer seems to matter.

                                                         Randy.