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Re: What qualifies as a constant ? (Was: Reverse sorting an array)

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On Friday, September 30, 2011 8:15:55 AM UTC-7, Mayeul wrote:
... 
> However, the example we're speaking about is not using an instance 
> constant. It is using a local constant variable. Now, without having 
> verified it, I expect such constants are not repeated any more than a 
> class constant would be.

It is repeated every time the method is invoked, semantically.

Operationally you'd expect a constant load, of course.  But my issue here is semantic.  If it's a constant, as in this example, the value cannot change between invocations or instances, so why scope it so narrowly?

One could argue as you do:
> I'd expect the point of that is to narrow the variable's scope down to 
> one single method. The point of /this/ would be... Well, questionable, 
> okay. I do that when I want to give a meaningful name to a constant 
> rather an a magical number, but the relevance of it only applies to one 
> single method. This usually only happens within classes I feel could be 
> refactored more clearly, though.

and I agree, particularly that the point is questionable.  More significantly it isn't consistent with convention and most style recommendations.  If something is a compile-time constant, it /should/ be declared at the class level, with static final constant variables.  Part of this is for maintenance - compile-time constants' class dependency rules differ from other variables (even final immutable ones that aren't compile-time constants).  You also get early assignment of 'final' member variables (including non-constant ones).  These are technical advantages for using true class-level constants, which though perhaps slight still combine with convention to trump a style argument for the questionable practice.

In summary:
- Upper-case names are limited to class-level constant variables by the core convention.
- Compile-time constant variables are treated differently from other variables, and such member variables particularly differently.
- The convention is to declare such constants as class member variables.
- Build and maintenance considerations support that convention for pragmatic reasons.
- Following the convention models the problem semantics more correctly.

-- 
Lew

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Reverse sorting an array Fred <albert.xtheunknown0@gmail.com> - 2011-09-30 04:03 -0700
  Re: Reverse sorting an array Eric Sosman <esosman@ieee-dot-org.invalid> - 2011-09-30 07:50 -0400
    Re: Reverse sorting an array Fred <albert.xtheunknown0@gmail.com> - 2011-09-30 15:24 -0700
      Re: Reverse sorting an array Eric Sosman <esosman@ieee-dot-org.invalid> - 2011-09-30 20:50 -0400
        Re: Reverse sorting an array Roedy Green <see_website@mindprod.com.invalid> - 2011-10-01 19:38 -0700
          Re: Reverse sorting an array Eric Sosman <esosman@ieee-dot-org.invalid> - 2011-10-01 22:58 -0400
            Re: Reverse sorting an array Lew <lewbloch@gmail.com> - 2011-10-01 20:21 -0700
    Re: Reverse sorting an array Fred <albert.xtheunknown0@gmail.com> - 2011-09-30 15:31 -0700
      Re: Reverse sorting an array Roedy Green <see_website@mindprod.com.invalid> - 2011-09-30 15:45 -0700
        Re: Reverse sorting an array Fred <albert.xtheunknown0@gmail.com> - 2011-09-30 16:27 -0700
          Re: Reverse sorting an array Patricia Shanahan <pats@acm.org> - 2011-09-30 16:58 -0700
    Re: Reverse sorting an array Roedy Green <see_website@mindprod.com.invalid> - 2011-09-30 15:43 -0700
      Re: Reverse sorting an array Eric Sosman <esosman@ieee-dot-org.invalid> - 2011-09-30 20:57 -0400
  Re: Reverse sorting an array Roedy Green <see_website@mindprod.com.invalid> - 2011-09-30 04:58 -0700
    What qualifies as a constant ? (Was: Reverse sorting an array) Mayeul <mayeul.marguet@free.fr> - 2011-09-30 14:45 +0200
      Re: What qualifies as a constant ? (Was: Reverse sorting an array) Lew <lewbloch@gmail.com> - 2011-09-30 07:39 -0700
        Re: What qualifies as a constant ? (Was: Reverse sorting an array) Mayeul <mayeul.marguet@free.fr> - 2011-09-30 17:15 +0200
          Re: What qualifies as a constant ? (Was: Reverse sorting an array) Lew <lewbloch@gmail.com> - 2011-09-30 08:42 -0700

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