(j3.2006) Problem with default expressions for kind type parameters?

[Van Snyder]

On Fri, 2012-09-21 at 08:04 -0500, Bill Long wrote:
> 
> 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)
> 
> I agree there is a problem with this statement.  The syntax for the part 
> enclosed by the ( ) following the type name is a <type-param-name-list> 
> in R426.   k+1 is not a "name".  Neither is something involving an "=".

Yeah, the problem is in the <type-param-decl>, not in the
<derived-type-stmt>.

> >      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>.
> 
> It appears that you are trying to prevent
> 
>    integer,kind :: j=K+1,  K=j+1
> 
> which would be a problem.

Malcolm has suggested "previously declared."  Right now, there is no
constraint on the <scalar-int-constant-expr> in <type-param-decl>.

> Cheers,
> Bill
> 
> >
> > 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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> >
>