define should be the keyword for manifest constants

[Russell Lewis]

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.

Russ