Re: Why only integer consts can be defined in the class?
* Thomas Richter:
{ Text reformatted in 72 columns. Please don't exceed 80 columns. -mod }
Adam Badura schrieb:
I don't see the reasons to forbid defining const static members of
other types then integer (especially when it comes to other basic
types like floating point). What are they then?
Static const members are of course designed to be optimized away by the
compiler when it sees the header. The problem with floating point
constants is that it depends on the implementation precision of the
compiler on which floating point number you get exactly. It might
depend. Thus, if you'd allow floating point constant members, you could
possibly create differing floating point constants depending on which
compiler is used. Consider now that you link the modules of two
different compilers (or even compiler versions) together. The result
might be pretty surprising.
The argument quoted above does not hold, since you can easily, although
very laboriously, achieve the same effect as a static double const
member initialized in the class.
// Implementing
// struct X
// { static double const foo = 3.14; }
template< typename Dummy >
struct FooConstant{ static double const foo; };
template< typename Dummy > double const FooConstant::foo = 3.14;
struct X: FooConstant<void> {};
Since the programmer can do the compiler's job, why can't the compiler
do it?
Saying that the above code will not support different compilers, well,
perhaps it doesn't, but if so, then almost no C++ code does.
Cheers, & hth.,
- Alf
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