(j3.2006) Specification functions

[Steve Lionel]

"I must not be the only one confused by this.  Our user documentation
explicitly prohibits a specification function from being recursive."

I can see how that misinterpretation could be made, but it is a mistake.
Nothing wrong with a specification function being recursive. You know where
to file the bug report. Tell Karen I said "Hi".

Steve

On Fri, Feb 24, 2017 at 5:13 PM, Steidel, Jon L <jon.l.steidel at intel.com>
wrote:

> I understand paragraph 6 prevents one from invoking the procedure which is
> being defined as a specification function inside itself (directly or
> indirectly).
>
>
>
> I must not be the only one confused by this.  Our user documentation
> explicitly prohibits a specification function from being recursive.
>
>
>
> -jon
>
>
>
> *From:* j3-bounces at mailman.j3-fortran.org [mailto:j3-bounces at mailman.j3-
> fortran.org] *On Behalf Of *Steve Lionel
> *Sent:* Friday, February 24, 2017 5:06 PM
> *To:* fortran standards email list for J3 <j3 at mailman.j3-fortran.org>
> *Subject:* Re: (j3.2006) Specification functions
>
>
>
> I read this as prohibiting a specification function from invoking the
> procedure in which it is used as a specification function, not prohibiting
> the specification function itself from being recursive.
>
>
>
> Steve
>
>
>
> On Fri, Feb 24, 2017 at 5:01 PM, Steidel, Jon L <jon.l.steidel at intel.com>
> wrote:
>
> References are to F2008 document (10-007r1)
>
> In section7.1.11 Specification expressions, paragraph 5 states
>
> "A function is a specification function if it is a pure function, is not a
> standard intrinsic function, is not an internal function, is not a
> statement function, and does not have a dummy procedure argument."
>
> Paragraph 5 goes on
>
> "Evaluation of a specification expression shall not directly or indirectly
> cause a procedure defined by the subprogram in which it appears to be
> invoked."
>
>  Note 7.32  which follows ends with a sentence
>
> "The prohibition against recursion avoids the creation of a new instance
> of a procedure while construction of one is in process."
>
> Nowhere in this section is there a prohibition against a recursive
> specification expression.  I scanned for occurrences of "recursi" and
> "specification expression" and found no prohibition of this elsewhere in
> the document.  I checked "Pure subprograms" and it appears a PURE
> subprogram may be recursive.   Should "is not a recursive function," be
> added to the list in paragraph 5?  Or should the last sentence of note 7.32
> be deleted?
>
> F2015 reads the same.  Since recursion is the default in 2015,
> specification functions in existing programs will need to be declared
> NONRECURSIVE if we really intended to disallow recursive specification
> functions.
>
> I see no harm in a recursive function being used to specify a dimension in
> an automatic array.
>
> -jon
>
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