define should be the keyword for manifest constants

[Derek Parnell]

On Thu, 13 Dec 2007 15:13:11 -0700, Russell Lewis wrote:

> Bill Baxter wrote:
>> Russell Lewis wrote:
>>> I thought about suggesting this, but what turned me off to it was this 
>>> declaration:
>>>
>>>     define int x = some_compile_time_func();
>>>
>>> A C/C++ programmer will probably think of this as a #define-style 
>>> substitution, which means that he will expect the function to run 
>>> every time that he uses the constant.  However, what we are trying to 
>>> declare is a manifest constant.  It seemed like it would introduce 
>>> confusion.
>> 
>> That may be their first guess as to what it does, but it doesn't seem 
>> like it would be difficult to relieve oneself of that misconception.
>> 
>> And in any case, the only time the above would work is if 
>> some_compile_time_function() really is a compile time function.  So it 
>> doesn't really matter if the user wants to think of it as evaluating 
>> every time it's used or just once.  That's the whole point of 
>> compile_time / pure functions.  No side effects and context doesn't matter.
> 
> I'm certainly not one who argues that we should take things from C/C++ 
> without reconsidering them! :)  I am just of the opinion that if we have 
> some other good choice for the keyword ("pure"), it is desirable not to 
> cause confusion.
> 
> IMHO, it's better for a C++ programmer to say "I've never seen that 
> keyword, let me look up what it does," than to say "I know what that 
> does" - and be wrong.  Yes, you can re-teach them.  But if the keyword 
> is unfamiliar, then you re-teach them the *first* time that they see it, 
> not ages later when they stumble upon a subtle bug.

Right ... like static, const, final, int, long, struct ... all used in
C/C++ but not in quite the same way.

-- 
Derek Parnell
Melbourne, Australia
skype: derek.j.parnell