Re: List Container Strawman 1.4

["Mark Lundquist" <no.spam@getalife.com>]

"Florian Weimer" <fw@deneb.enyo.de> wrote in message
news:87heqs5awc.fsf@deneb.enyo.de...
> Ted Dennison<dennison@telepath.com> writes:
>
> > I have posted a strawman version 1.4 of the standard Ada List container
at
> > http://www.telepath.com/dennison/Ted/Containers-Lists-Unbounded.ads.html
.
>
>
>    -- List <---> Unconstrained array conversions.
>
>    type Element_Array is array (Natural range <>) of Element;
>
>    function To   (Source : Element_Array) return List;
>    function From (Source : List) return Element_Array;
>
> What about a generic version of To and From which can handle arrays
> with different index types?

Interesting idea, but I doubt if it would be useful enough to be justified.
A list abstraction of this sort is unbounded, and since the only reason you
would convert To it from one of these things with a non-integer index type
would be to convert From the list back to it again, you're not going to be
adding or deleting elements... using a list this way (e.g. to find or sort)
is quite roundabout, it would be much better to have a Fixed variant of the
sequence abstraction.

'To' is probably much more useful than 'From', in any case (you can use an
aggregate notation to initialize your list).

>
>    -- Passive iterator. Operation will be applied on each element on the
list
>    -- Opertion can terminate this process early by setting Quit to True.
>
>    generic
>       with procedure Operation (Target : in out Element; Quit : out
Boolean);
>    procedure Passive_Iterator (Target : in out List);
>
>
> I'd like to suggest to make Quit mode "in out", with a default of
> False.

There are no defaults for anything other than an "in" mode parameter.

>
>    -- Sorting sub-package.
>    -- To sort in increasing order, use the ">" routine for the
Reverse_Order
>    -- parameter. To sort in decreasing order, substitute your "<" routine
for
>    -- the Reverse_Order parameter. :-)
>
> I think the Reverse_Order predicate should be named differently, so
> that it's clear from its name that it's a predicate.  "Reverse_Order"
> could also mean "Reverse the order of the elments.", not just "Are
> these elements in reversed order?".

I must say I don't care much for these attempts to avoid using a relational
operator for the predicate ("Swap", "Reverse_Order").  They are a case of
the cure being worse than the disease.  Besides being obtuse and
bletcherous, they lack the notational convenience provided by a relational
operator with a box (<>) default.

-- mark