Re: overload ":=" ???

[jsa@alexandria (Jon S Anthony)]

In article <31ED3F5F.1135B4EA@jinx.sckans.edu> David Morton <dmorton@jinx.sckans.edu> writes:

> Is there a way to overload the assignment operator ":=" ?

Not exactly, but you can typically get close to equivalent
functionality with controlled types (RM 7.6 "User-Defined Assignment
and Finalization")

However, your example is something where a "converter" would be the
more natural approach in Ada.

> with Text_IO; use Text_IO;
> procedure Test is
> type Text;
> type Text_Ptr is access Text;
> 
> type Text is record
>    Buf : String(1..50);
>    Length : Natural;
> end record;
>
> function ":="(Right : String) is

function to_text ( right : string ) return text is
    res : text;
begin
    if right'length > text.buf'length then
        raise ...
    else
        res.buf(right'range) := right;
        res.length := right'length;
    end if;
    return res;
end to_text;

...

    t : text := to_text("hi there!");

A variation that some use is to name the "to_text" function as a unary
operator like "+" or something.  Then you get:

    t : text := +"hi there!";

/Jon
-- 
Jon Anthony
Organon Motives, Inc.
1 Williston Road, Suite 4
Belmont, MA 02178

617.484.3383
jsa@organon.com