(j3.2006) Problem with default expressions for kind type parameters?
Van Snyder
Van.Snyder
Fri Sep 21 16:38:18 EDT 2012
On Fri, 2012-09-21 at 10:47 -0500, Bill Long wrote:
> Revising Van's example leads to another question:
>
> type t(j,k)
> integer,kind :: j = 5
> integer,kind :: k = j+1
> end type t
>
> type(t) :: v
> type(t(j=10)) :: w
> print *, v%j, v%k
> print *, w%j, w%k
> end
>
> Assuming this is allowed at all, what is expected for w%k? I could see
> an argument for either 6 or 11. I think it would be better to just
> restrict the initialization expressions for a KIND type parameter in a
> type definition to be a scalar integer constant.
I don't see an argument for w%k == 6.
> Cheers,
> Bill
>
>
> On 9/20/12 10:17 PM, Van Snyder wrote:
> > A type parameter name in a type definition is a valid primary in a
> > constant expression (7.1.12p1(9)).
> >
> > One need not specify kind type parameter values in the declarations of
> > objects of a type if there is a default in the type definition.
> >
> > There appears to be a problem with this:
> >
> > type :: T(J=k+1,K=j+1)
> > integer, kind :: J, K
> > end type T
> >
> > type(t) :: V
> >
> > Do we need a constraint something like this?
> >
> > C438a (R431) There shall not be a circular dependence between a
> > <scalar-int-constant-expr> in a <type-param-decl> and any
> > <type-param-name> in the same <type-param-decl-list>.
> >
> > A bigger hammer, perhaps larger than necessary, is
> >
> > C438a (R431) A <type-param-name> shall not appear in a
> > <scalar-int-constant-expr> in the same <type-param-decl-list>.
> >
> > A medium-size hammer, easier to check than the first one, is
> >
> > C438a (R431) A <type-param-name> that appears in a
> > <scalar-int-constant-expr> in a <type-param-decl-list> shall
> > be declared earlier in that <type-param-decl-list>.
> >
> > I think this is the tiniest hammer that works (maybe):
> >
> > C485a (R453) If there is a circular dependence between a
> > <scalar-int-constant-expr> in a <type-param-decl> and any
> > <type-param-name> in the same <type-param-decl-list>, a
> > <type-param-value> shall be provided for at least one of
> > the <type-param-name>s in the circular dependency relationship.
> >
> >
> > _______________________________________________
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> >
>
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