J3/17-123r2
To: J3
From: Malcolm Cohen & Daniel Chen & Toon Moene
Subject: Why are team specifiers always variables?
Date: 2017 February 14


1. Introduction
---------------

Team specifiers are required to be variables (nearly?) everywhere, even
where they are not being modified.  This prevents the user from using a
function that returns TYPE(TEAM_TYPE) in such places; instead, he needs
to assign the value to a temporary variable.

This restriction does not appear to be necessary or useful.


2. Discussion
-------------

The most obvious places where this would be useful are CHANGE TEAM and
SYNC TEAM.  In particular, the latter requires the user to write something
like
    tmp = GET_TEAM(PARENT_TEAM)
    SYNC TEAM ( tmp )
instead of the simpler
    SYNC TEAM ( GET_TEAM(PARENT_TEAM) )

Requiring the user to assign the value of GET_TEAM and any function he
writes that returns a TEAM_TYPE value is inconvenient and arguably
error-prone.

Similarly, for CHANGE TEAM, if the user has a team selection function,
he needs to write
    tmp = select_team(...)
    CHANGE TEAM ( tmp )
instead of the simpler
    CHANGE TEAM ( select_team(...) )

Admittedly the use case for this is slightly weaker than SYNC TEAM, and
CHANGE TEAM is where the team-variable BNF is defined, making edits to
that slightly more complicated.

Finally, the edits contain some cosmetic changes because team-variables do
not "specify" a team, they "identify" a team, according to paragraph 2 of
16.10.2.32 TEAM_TYPE.


3. Image selectors
------------------

It might be unlikely that anyone will really want to use a function
reference in the TEAM= specifier of an image selector, but it would be
consistent and easy to change this as well.  Edits to do this are at
the end of the paper.


4. Edits to 17-007 to do both CHANGE TEAM and SYNC TEAM
-------------------------------------------------------

[187:8] 11.1.5.1 Purpose and form of the CHANGE TEAM construct,
        R1112 change-team-stmt,
        Change "<team-variable>" to "<team-value>".

[187:12] Same subclause, R1115 team-variable,
         Change "<team-variable> <<is>> <scalar-variable>"
         to     "<team-value> <<is>> <scalar-expr>".

[187:23] Same subclause, C1115 "A team-variable shall",
         Change "A <team-variable> shall"
         to     "A <team-value> shall".

[188:6,8-9] 11.1.5.2 Execution of a CHANGE TEAM construct, p1
  Change "The values of the <team-variable>s"
  to     "The <team-value>s",
  Change "specified by the value of <team-variable>"
  to     "identified by <team-value>".
{Note cosmetic change in the edit.}

[188:9-10] 11.1.5.2 Execution of a CHANGE TEAM construct, p1, sentence 3,
       Replace the sentence beginning  "The current team is not changed"
       with
       "If <team-value> is a variable, the current team is not changed
        by a redefinition of that variable during execution of the
        CHANGE TEAM construct."

[188:22] Same subclause, p6
         Change "identified by <team-variable>"
         to     "identified by <team-value>".

[213:2] 11.6.6 SYNC TEAM statement, R1169 sync-team-stmt,
        Change "<team-variable>" to "<team-value>".

[213:3] Same subclause, p1,
  Change
    "The <team-variable> shall be defined with a value that represents"
  to
    "The <team-value> shall identify"
  making the whole paragraph read
    "The <team-value> shall identify an ancestor team, the current team,
     or a team whose parent is the current team."
{Note cosmetic change in the edit.}

[213:5-6] Same subclause, p2,
          Change "the team specified by <team-variable>"
          to     "the team identified by <team-value>"
{Note cosmetic change in the edit.}

[214:17+] 11.6.9 FORM TEAM statement, after R1176 team-number,
          insert new BNF and constraint
  "R1176a <team-variable> <<is>> <scalar-variable>
   C1176a A <team-variable> shall be of type TEAM_TYPE from the intrinsic
          module ISO_FORTRAN_ENV."
{Reinstate BNF for team-variable in the appropriate place.}

[214:24] Change "specifies" to "identifies"
{The value of a team variable identifies a team; it does not specify a
team.}


5. Edits for the image selector TEAM= specifier
-----------------------------------------------

[139:19] 9.6 Image selectors, R926 image-selector-spec,
  Change
    "TEAM = <team-variable>"
  to
    "TEAM = <team-value>".

[139:28-29] Same subclause, p3,
  Change
    "the team of the image selector is specified by <team-variable>,
    which shall be defined with a value that represents the current or
    an ancestor team;"
  to
     "the <team-value> shall identify the current or an ancestor
     team;"

  making that sentence read

    "If a TEAM= specifier appears in an image-selector, the team-value
     shall identify the current or an ancestor team; the object shall be
     an established coarray in that team or an ancestor thereof."
{Note cosmetic change in the edit.}

===END===