"Moving" objects of limited type

"Moving" objects of limited type

[Florian Weimer]

For some limited types, it seems to be worthwhile to have an operation
which moves the "value" (whatever this means) from one location to
another, destroying the original "value".  Usually, this is much
more efficient than a traditional "copy" where the "value" has to be
duplicated.

For a concrete example, consider a limited string type where the
actual characters are allocated on the heap.  This operation could be
described in the following way:

   procedure Do_Something
     (Source : in out Mutable_String;
      Target : in out Mutable_String);
   --  Assign the value of Source to Target, and then assign the
   --  empty string to Source.  This is much faster than Copy, but it
   --  destroys the Source object.

Now my question: What's an appropriate name for such an operation?
"Move", "Relocate", "Rename", "Teleport"?  Maybe this operation is
quite common, and in this case I want to use the correct term.

Re: "Moving" objects of limited type

[Nick Roberts]

I would suggest:

   procedure Transfer (From, To: in out Object_Type) [is abstract];

If you are worried that the word 'transfer' might be interpreted as meaning
'swap', you could use the parameter names to counteract this, e.g.:

   ...
   Saved_Text := Working_Text; -- makes copy
   Beautify(Working_Text);
   if not User_Agrees then
      Transfer(From => Saved_Text, To => Working_Text);
   else
      Saved_Text := Empty_Text; -- deletes
      ...

It is perhaps curious to note how this example could be interpreted as a
demonstration of how 'ugly'* the classic ":=" assignment notation is.
(Personally, I find ":=" too readable to be so condemned. If nothing else,
it helps break up the code.)**

--
Nick Roberts
http://www.adapower.com/lab/adaos

*e.g. inconsistent with the general form of procedure call

**Reading Pascal Obry's reply, I would sometimes find whole pages of Cobol
(in OFPC***) consisting entirely of MOVEs, in times gone by. Nobody had
taught them MOVE CORRESPONDING. Sad.

***Other Funny Programmers' Code


"Florian Weimer" <fw@deneb.cygnus.argh.org> wrote in message
news:87wvk6xz5p.fsf@deneb.cygnus.argh.org...

> ...
> Now my question: What's an appropriate name for such an operation?
> "Move", "Relocate", "Rename", "Teleport"?  Maybe this operation is
> quite common, and in this case I want to use the correct term.

Re: "Moving" objects of limited type

[Pascal Obry]

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Florian Weimer a �crit dans le message
<87wvk6xz5p.fsf@deneb.cygnus.argh.org>...
>Now my question: What's an appropriate name for such an operation?
>"Move", "Relocate", "Rename", "Teleport"?  Maybe this operation is
>quite common, and in this case I want to use the correct term.

I have never seen this operation but I would name it "Relocate".

I don't like "Move" as it has sometime been used for a copy, if
my memory is correct the Move operation in COBOL is a copy.
(ok, I've never been -and by far- a COBOL expert but sometimes
 you have something anchored in your memory...)

Pascal.

--|------------------------------------------------------
--| Pascal Obry                           Team-Ada Member
--| 45, rue Gabriel Peri - 78114 Magny Les Hameaux FRANCE
--|------------------------------------------------------
--|         http://perso.wanadoo.fr/pascal.obry
--|
--| "The best way to travel is by means of imagination"

Re: "Moving" objects of limited type

[Marin D. Condic]

Florian Weimer wrote:
> Now my question: What's an appropriate name for such an operation?
> "Move", "Relocate", "Rename", "Teleport"?  Maybe this operation is
> quite common, and in this case I want to use the correct term.

I think you want to avoid "Move" since Ada.Strings... uses "Move" to
mean "Copy". "Relocate" or "Transfer" sound like they describe the
behavior and don't come with baggage that may cause misinterpretation.

MDC
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