To: J3                                                     J3/24-163r3
From: generics
Subject: Edits for TEMPLATE construct
Date: 2024-October-29
References: 24-161, 24-162, 24-125r5, 24-126r4, 24-127r4

Introduction:
=============

This is the 3rd of 6 papers that provide edits for the approved syntax
for templates.

Note that the section numbering is merely suggestive.  The overall
ordering of template subclauses will change in future papers, and
clause 15 itself is merely a placeholder.

Section 1:
==========

* Append the following at the end of clause 15 from paper 24-162.


15.3 The TEMPLATE construct

15.3.1 Syntax for the TEMPLATE construct

A TEMPLATE construct defines a template that may define multiple
entities which may be accessed through instantiation.

R1510 <template> <<is>> <template-stmt>
                        [ <template-specification-part> ]
                        [ <template-subprogram-part> ]
                        <end-template-stmt>

C1527a (R1510) A <template> shall only appear in the <specification-part>
               of a main program or module.

R1511 <template-stmt> <<is>>
          TEMPLATE <template-name> ([<deferred-arg-list>])

R1512 <end-template-stmt> <<is>>  END TEMPLATE [<template-name>]


C1527b (R1512) If a <template-name> appears in the <end-template-stmt>,
               it shall be identical to the <template-name>
               specified in the <template-stmt>.

15.3.2 Template specification part

R1513 <template-specification-part> <<is>>
          [ <use-stmt> ] ...
          [ <import-stmt> ] ...
          [ <template-declaration-construct> ] ...

The implicit mapping within <template> is as if
       IMPLICIT NONE(TYPE,EXTERNAL)
is specified.

R1514 <template-declaration-construct>
          <<is>> <template-specification-construct>
          <<or>> <deferred-arg-decl-stmt>
          <<or>> <requirement>
          <<or>> <template>

R1515 <template-specification-construct>
          <<is>> <access-stmt>
          <<or>> <derived-type-def>
          <<or>> <dimension-stmt>
          <<or>> <enum-def>
          <<or>> <enumeration-type-def>
          <<or>> <generic-stmt>
          <<or>> <instantiate-stmt>
          <<or>> <interface-block>
          <<or>> <intrinsic-stmt>
          <<or>> <parameter-stmt>
          <<or>> <type-declaration-stmt>

C1528 (R1515) An entity declared by <type-declaration-stmt> shall
              have the PARAMETER attribute.

NOTE 1

    ALLOCATABLE, ASYNCHRONOUS, BIND, CODIMENSION, COMMON, CONTIGUOUS,
    DATA, ENTRY, EQUIVALENCE, EXTERNAL, FORMAT, INTENT, NAMELIST,
    OPTIONAL, POINTER, PROTECTED, SAVE, TARGET, VOLATILE, VALUE, or
    statement function statements cannot appear in a template
    specification section.

NOTE 2

    A template specification section cannot declare variables.

15.3.3 Template subprogram part

R1516 <template-subprogram-part> <<is>> <contains-stmt>
                                        [ <template-subprogram> ] ...

R1517 <template-subprogram>
          <<is>> <function-subprogram>
          <<or>> <subroutine-subprogram>
          <<or>> <templated-function-subprogram>
          <<or>> <templated-subroutine-subprogram>

15.4 Templated procedures

A templated procedure is a template that defines a single
procedure which is accessible via instantiation.


R1518 <templated-function-subprogram> <<is>>
          <templated-function-stmt>
          <templated-subprogram-specification-part>
          [<execution-part>]
          [<internal-subprogram-part>]
          <end-function-stmt>

C1529 (R1518) If a <function-name> appears in the <end-function-stmt>,
              it shall be identical to the <template-name>
              specified in the <templated-function-stmt>.

R1519 <templated-subroutine-subprogram> <<is>>
          <templated-subroutine-stmt>
          <templated-subprogram-specification-part>
          [<execution-part>]
          [<internal-subprogram-part>]
          <end-subroutine-stmt>

C1530 (R1519) If a <subroutine-name> appears in the <end-subroutine-stmt>,
              it shall be identical to the <template-name>
              specified in the <templated-subroutine-stmt>.

C1531 An internal templated procedure shall not contain an
      <internal-subprogram-part>.

{UTI: I seem to recall that we wanted to prohibit nested templated
procedures.  Do we? I can't find any constraint to prohibit
that. Should we add

C1532 The <internal-subprogram-part> of a templated procedure shall not
      conatain a <templated-function-subprogram> or
      <templated-subroutine-subprogram>.
}

R1520 <templated-subprogram-specification-part> <<is>>
          [ <use-stmt> ] ...
          [ <import-stmt> ] ...
          [ <templated-subprogram-declaration-construct> ] ...

R1521 <templated-subprogram-declaration-construct>
          <<is>> <deferred-arg-decl-stmt>
          <<or>> <format-stmt>
          <<or>> <specification-construct>

R1522 <templated-function-stmt> <<is>>
          [ <prefix> ] FUNCTION <template-name>
          ( <deferred-arg-list> ) ([<dummy-arg-list>])
          [<suffix>]

R1523 <templated-subroutine-stmt> <<is>>
         [ <prefix> ] SUBROUTINE <template-name>
         ( <deferred-arg-list> ) ([<dummy-arg-list>])
         [<proc-language-binding-spec>]

15.5 Restrictions on template definitions

C1533 A variable or procedure pointer declared in either a
      <template-subprogram-part> or a
      <templated-subprogram-declaration-construct> shall
      not have the SAVE attribute.

C1534 EQUIVALENCE and COMMON shall not appear in a
      <template-subprogram-part> or a
      <templated-subprogram-declaration-construct>.

{UTI: Should we just say "EQUIVALENCE and COMMON shall not appear within
      a template or templated procedure? In particular, C1534 does not
      cover the case of
         MODULE M
         CONTAINS
             SUBROUTINE tmplsub(T)(x)
             CONTAINS
                 SUBROUTINE internal_nontemplate_sub()
                     COMMON ...
                     EQUIVALENCE ...
                 END SUBROUTINE
             END SUBROUTINE
         END CONTAINS
      because internal_nontemplate_sub does not have a
      <templated-subprogram-declaration-construct>

     Same goes for C1533 and the SAVE attribute.
}

C1535 <template>, <templated-function-subprogram> and
      <templated-subroutine-subprogram> shall only
      reference intrinsic procedures, procedures with explicit
      interfaces, operators, or intrinsic assignment.

NOTE

    This constraint expresses the notion of type-safety.  In particular,
    this allows a template implementation to be verified to be internally
    consistent.

===END===