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From: Brian Drummond <brian@shapes.demon.co.uk>
Newsgroups: comp.lang.ada
Subject: Re: What would you like in Ada202X?
Date: Sat, 30 Jun 2012 17:00:46 +0000 (UTC)
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Date: 2012-06-30T17:00:46+00:00
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On Sat, 30 Jun 2012 14:34:10 +0200, Dmitry A. Kazakov wrote:

> On Sat, 30 Jun 2012 12:00:13 +0000 (UTC), Brian Drummond wrote:
> 
>> One obvious problem with an extensible set of operators, in an operator
>> precedence grammar, is assigning the precedence level of new operators.
> 
> Ada actually solved that by making associations of operators in question
> illegal. E.g. a or b and c. "or" cannot share argument with "and".

So one (simple but restrictive) solution would be to extend this 
"unrelated precedence" to all new operators.

> Operators conflicting with identifiers will impose a serious problem.

I was not expecting such operators to be permitted. Alphanumeric 
characters would not be among the set of characters available for the 
purpose.

(a **** b) might be permitted, (a f*** b) would surely not!

> http://en.wikipedia.org/wiki/
Mathematical_operators_and_symbols_in_Unicode
> 
> A subset or all of them would suffice.
> 
>> I can't see any fundamental drawbacks.
> 
> Code review and maintainability problems. The set of symbols cannot be
> infinite.

Practical considerations surely restrict the length of additional 
operators, but I'm not sure that restriction belongs in the syntax.

- Brian