Invalid operator name?

Invalid operator name?

[Sandro Magi]

When I try to define my own operator, I receive an "Invalid operator name"
error during compilation. I've found references to operator overloading in
reference materials, but no word whether new operators can be defined which
leads me to believe that it's not possible.

Is it not possible to define new operators for a custom type? Can we only 
override the base operators?

Re: Invalid operator name?

[Stephen Leake]

Sandro Magi <smagi@naasking.homeip.net> writes:

> When I try to define my own operator, I receive an "Invalid operator name"
> error during compilation. I've found references to operator overloading in
> reference materials, but no word whether new operators can be defined which
> leads me to believe that it's not possible.

Right; only the predefined operators may be overloaded. That
simplifies the front end of the Ada parser, and makes it easier for
everyone to read your code.

-- 
-- Stephe

Re: Invalid operator name?

[Martin Krischik]

Sandro Magi wrote:

> When I try to define my own operator, I receive an "Invalid operator name"
> error during compilation. I've found references to operator overloading in
> reference materials, but no word whether new operators can be defined
> which leads me to believe that it's not possible.
> 
> Is it not possible to define new operators for a custom type? Can we only
> override the base operators?

Right, only the base operators can be overloaded.  See the following list:

http://en.wikibooks.org/wiki/Programming:Ada:Operators

However, Operators can be overloaded by Return type as well. See some of the
options used for "*", where the "*" operator my return a String,
Bounded_String or Unbounded_String depending on destination type.

http://en.wikibooks.org/wiki/Programming:Ada:Operators:*

But beware: to exotic uses for operators make the code more hard to read!

With Regards

Martin
-- 
mailto://krischik@users.sourceforge.net
http://www.ada.krischik.com

Re: Invalid operator name?

[David C. Hoos, Sr.]

As with many of the questions posed in this newsgroup, the
answer is given explicitly in the Ada Reference Manual.

Allow me to quote the relevant excerpt:

4.5 Operators and Expression Evaluation

1 The language defines the following six categories of operators (given in order of increasing 
precedence). The corresponding operator_symbols, and only those, can be used as designators in 
declarations of functions for user-defined operators. See 6.6, "Overloading of Operators".

Syntax

2 logical_operator ::=  and  |  or  |  xor
3 relational_operator ::=  =  |  /=  |  <  |  <=  |  >  |  >=
4 binary_adding_operator ::=  +  |  -  |  &
5 unary_adding_operator ::=  +  |  -
6 multiplying_operator ::=  *  |  /  |  mod  |  rem

7 highest_precedence_operator ::=  **  |  abs  |  not

Please note the words "and only those" near the middle of the second line of 4.5(1)

----- Original Message ----- 
From: "Sandro Magi" <smagi@naasking.homeip.net>
Newsgroups: comp.lang.ada
To: <comp.lang.ada@ada-france.org>
Sent: November 27, 2004 10:23 AM
Subject: Invalid operator name?


> When I try to define my own operator, I receive an "Invalid operator name"
> error during compilation. I've found references to operator overloading in
> reference materials, but no word whether new operators can be defined which
> leads me to believe that it's not possible.
>
> Is it not possible to define new operators for a custom type? Can we only
> override the base operators?
> _______________________________________________
> comp.lang.ada mailing list
> comp.lang.ada@ada-france.org
> http://www.ada-france.org/mailman/listinfo/comp.lang.ada
>
>