Re: global variables - an alternate approach

From:
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Newsgroups:
comp.lang.c++.moderated
Date:
Sun, 14 Feb 2010 17:27:14 CST
Message-ID:
<6942653e-0bf2-4469-854d-e8b6b6650bb9@q16g2000yqq.googlegroups.com>
On Feb 13, 6:24 pm, "Martin B." <0xCDCDC...@gmx.at> wrote:

You did *not* define global variables, but global constants.

OK! I'll buy that.

In you case I would do:
namespace my_consts {
static int const a = 5;
static double const pi = 3.141;

}


True but of course - if memory serves - this violates the ODR rule.
Every translation unit that include either (common_data_a.h or
common_data_b.h) file will get a/their own copy of 'a' and 'PI'

The singleton approach makes sense when your global object (be it a
const or a variable) should only be constructed if used:

class MyConsts {
const LargeInteger a;
const RealNumber pi;
MyConsts()
: a("5000100200300400500600700800900")
, pi("3.14159265358979323846264338327950288")
{ }
public:
MyConsts const& instance() {
// Threading issues aside, this will only call the ctor of MyConsts
// the first time instance() is called:
static MyConsts obj;
return obj;
}

};

Agreed!

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