From: david.brown@hesbynett.no
On 29/11/2025 12:24, bart wrote:
> On 29/11/2025 03:38, Keith Thompson wrote:
>> bart writes:
>>> On 28/11/2025 23:23, Keith Thompson wrote:
>>>> bart writes:
>>>>> On 28/11/2025 02:33, Janis Papanagnou wrote:
>>>> [...]
>>>>>> You can of course add as many commodity features to "your language"
>>>>>> as you like. I seem to recall that one of the design principles of
>>>>>> "C" was to not add too many keywords. (Not sure whether 'A.odd' is
>>>>>> a function or keyword above [in "your language"].)
>>>>>
>>>>> It is a reserved word, which means it can't be used as either a
>>>>> top-level user identifier, or a member name. With extra effort, it
>>>>> could be used for both, but that needs some special syntax, such as
>>>>> Ada-style "A'odd"; I've never got around to it.
>>>>>
>>>>> In Pascal (where I copied it from) it is a reserved word.
>>>> In Pascal, "odd" is not a reserved word. It's the name of a
>>>> predefined function.
>>>
>>> So what's a 'reserved word' then? To me it is something not available
>>> as a user-identifier because it has a special meaning in the language,
>>> which may be that of a predefined function among other things.
>>
>> Right. The name "odd" is available as a user-defined identifier.
>> If you define something named "odd" in Pascal, it hides the
>> predefined function of that name.
>
> I did test it with a toy Pascal compiler I have. Defining 'odd' as a
> variable didn't work, but that was for other reasons.
>
>
>> You can think of Pascal's predefined functions as being declared
>> in an outer scope, surrounding the main program.
>
> I took 'predefined functions' to mean 'built-in functions' (effectively,
> operators with function-like syntax), that cannot be overridden.
>
> So 'odd' is not a reserved word in Pascal; I was mistaken.
>
> (My opinion is that being able to shadow fundamental language features
> is undesirable. Being able to reuse them as user identifiers is another
> matter, but that would involve tricks with syntax or context to avoid
> ambiguity.)
>
>
The issue is where you draw the line of what is a "fundamental language
feature", and what is not. For Pascal, "begin" is a fundamental
language feature, part of the syntax. "odd" is not fundamental - it's
just a function in the Pascal's equivalent of the C standard library.
So no tricks or special syntax (like "stropping") are needed to re-use
the identifier for other purposes.
I agree that using words that are "fundamental" is not good. But if a
language provides built-in functions in a global namespace, then it is a
serious limitation if these cannot be shadowed or overridden.
Basically, it means that you are always at risk of conflicts with
existing code if later language versions add new functions. So if
someone wrote Pascal code with a local variable called "even", and a
later version introduced a built-in function "even", then it is critical
that this is an overrideable or shadowable (if that is a real word!)
identifier.
That's why C is very conservative about adding new keywords, and uses
reserved namespaces for the purpose - thus C99 added "_Bool", not
"bool", to avoid conflict with existing code. Only now, over two
decades later, did the committee feel that uses of the identifier "bool"
other than as a typedef for _Bool (usually via ) are so rare
that C23 could finally have "bool" as a keyword for the type. And they
still have challenges with good names for standard library functions -
now in C23, many new ones have names with a "stdc_" prefix.
--- SoupGate-Win32 v1.05
* Origin: you cannot sedate... all the things you hate (1:229/2)
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