From Rosetta Code
Latest comment: 14 years ago by Dmitry-kazakov in topic Constants

Similarity to Scope modifiers

Is it just me or is this task really similar to Scope modifiers? Maybe they needs to be merged? I may be crazy. --Mwn3d 20:55, 16 July 2009 (UTC)Reply[reply]

I see what you mean. --Paddy3118 02:49, 17 July 2009 (UTC)Reply[reply]

So what's the plan? --Mwn3d 01:24, 27 July 2009 (UTC)Reply[reply]


I'm wondering if it would be worth it to either add constants to this task, or make another, related task for declaring constants. Something like:

Show how to declare a constant (i.e. a variable that can't be changed after being declared).

(I'm thinking of constants as opposed to literals, like const int x = 1 or even #define x 1 rather than just 1.) Y'know, the things that you use instead of magic numbers. -- Eriksiers 17:41, 20 October 2009 (UTC)Reply[reply]

(This, of course, assumes that there isn't already a constants page on here somewhere.) -- Eriksiers 18:34, 20 October 2009 (UTC)Reply[reply]

If the task is here, it's not where I'd put it (Category:Basic language learning). I think it might be good to add it. Though if this task stays intact (see dispute above) it might be better to add it here. --Mwn3d 18:38, 20 October 2009 (UTC)Reply[reply]
The above dispute is why I asked first, rather than just doing it. -- Eriksiers 18:42, 20 October 2009 (UTC)Reply[reply]
"The things that you use instead of magic numbers" might be a naming convention on otherwise standard variables? --Paddy3118 18:49, 20 October 2009 (UTC)Reply[reply]
Perhaps I phrased it poorly here. I'm specifically referring to "variables" that aren't variable, i.e. things declared const in C or BASIC, like in my example above. Not just a naming convention, but part of the language. -- Eriksiers 01:04, 21 October 2009 (UTC)Reply[reply]

There are two things in it:

  • a value, denoted in some way, e.g. by a literal, by an identifier (named constant), by a static expression (evaluated at compile time);
  • an object, maybe of an immutable subtype.

The term "constant" may refer to either. In C const is a type modifier that produces an immutable subtype of the type it precedes. When used in declarations it does an immutable object, e.g. the second thing. But the compiler has right to convert it into the first thing, e.g. not to allocate any objects, but use the corresponding value instead, of course when the value is static. This conversion is semantically valid, when object construction and finalization have no semantically "visible" side effects (memory allocation, CPU cycles are semantically "invisible"). The bottom line is that IMO const belongs to the tasks dealing with types rather than to variables having those type. --Dmitry-kazakov 13:56, 22 October 2009 (UTC)Reply[reply]