🚀 go-pugleaf

clamage@Eng.Sun.COM (Steve Clamage) wrote:

>In article 95Oct26140846@avs.cs.rpi.edu, vandevod@cs.rpi.edu (David Vandevoorde
>) writes:
>>
>>>>>>> "SC" == Steve Clamage <clamage@eng.sun.com> writes:
>>[...]
>>SC> You can use the enum hack, but it isn't necessary. You can now (if
>>SC> your local compiler supports the change) declare a static member of
>>SC> any integral type as a manifest constant:
>>[...]
>>
>>Would you happen to know why it must be an ``integral type''?
>>I imagine uses for floating-point constants...
>
>I believe it is because integral constant-expressions are a special item
>in the language.  A floating-point constant-expression may consist only
>of floating-point literals. For example, at file scope:
>
>	const int two = 2; // 'two' is a constant-expression
>	int k = two; // OK
>
>	const double pi = 3.1415926535798;
>	double x = pi; // error, 'pi' is not a constant-expression
>
>So it seems to me that being able to write
>	struct T { static const double e = 2.7182818285; };
>doesn't give you any added capability or convenience compared to
>	struct T { static const double e; };
>because you must still provide a definition someplace.
>
>We might someday revisit the restrictions on floating-point constants,
>but it seems to me the rules are at least consistent.


Am I confused?  I thought that initializers of non-aggregates could be
any expressions, not just constant expressions and that

	double x - pi;

above was legal.

Michael M Rubenstein


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