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From: Brian Drummond <brian3@shapes.demon.co.uk>
Newsgroups: comp.lang.ada
Subject: Re: 'Image (was: What exactly is the licensing situation with
 GNAT?)
Date: Wed, 19 Nov 2014 13:46:41 +0000 (UTC)
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Date: 2014-11-19T13:46:41+00:00
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On Sat, 15 Nov 2014 20:58:39 +0100, Georg Bauhaus wrote:

> On 15.11.14 18:32, Florian Weimer wrote:
>> * Randy Brukardt:
>>
>>> Semi-related to this is that we approved Obj'Image as a
>>> language-defined attribute,

>> Did they drop leading space characters while they were at it? :-)
> 
> Of course not, they know about the possibility of a '-', and how are you
> going to write orderly column layout if in Ada there is no space!
> 
> Perfect ground for debate.
> 
> Will 'Image be user definable?  Like Python's __str__? Very good for
> obfuscation, then. Will the encoding be part of the definition,
> so that I can use it in our existing trace logs?

Something similar just came up in a VHDL context, where the question was 
asked, is '&' overloadable for non-string-or-character types. 

And it appears it is, so that you can simplify the creation of 
complicated strings (and eliminate leading spaces if you wish) by a 
package of functions overloading '&' to wrap 'Image for integer and 
similar types.

The testcase (minimally translated) seems to work in Ada too (Gnat 4.9.1 
at least), extension from single characters to 'image and strings should 
be obvious.

--------------------------------------------------------
with Ada.Text_IO;

procedure foo is
    function "&" (l: string; r: natural) return string is  
    begin
        return  l & character'VAL(r);
    end "&";
    
    a: constant string := "abcd";
    b: constant string := "efgh";
begin
    Ada.Text_IO.put_line( "concatenated string is " & a &  -- Line 18 
            character'VAL(16#42#) & b & 
            "  " &  a & 16#42# & b );
end foo;
--------------------------------------------------------

-- Brian