J3/15-101r1
To:       J3
Subject:  Wart removal proposal -- Specification expressions
From:     Van Snyder
Date: 2015 February 24
Reerence: 15-007

1. Introduction
===============

The question whether such things as

  integer :: B = bit_size(B)

are permitted or prohibited has recently recurred on comp_lang_fortran.

Interp F95/000090 (why did we have six-digit interp numbers?) included
the above example, and several others, including

  character :: C(20)*(size(C,1))

The answer to the interp was that both of these declarations (and
several additional examples) were intended to be illegal.  This resulted
in 7.1.11p8, which says, in part

  "The prior specification may be to the left of the specification
   inquiry in the same statement, but shall not be within the same
   <entity-decl>..."

which is somewhat ambiguous: It is reasonable that the extents of an
array might not be established before before a <char-length> is
examined, as in the second example, but certainly one knows the type and
type parameters before processing any <entity-decl> in the statement.
I.e., is the bit size specified by the <entity-decl> or the
<declaration-type-spec>?

2. Specification
================

Allow properties of an object to be referenced within its
<initialization>, provided the properties depend only upon the type and
kind type parameters of the object.

This would allow such things as

  integer :: B = bit_size(B)
  real :: E = sqrt(sqrt(epsilon(E)))

3. Syntax
=========

The proposal is germane to R503 <entity-decl> and R505 <initialization>,
but no syntax rules are changed.

4. Edits
========

[156:30 7.1.12p2] Append to end of the sentence:
  ", unless the specification inquiry appears within an <initialization>
   and the properties depend only on the type and kind type parameters".

5. Alternative Specification
============================

Allow to reference any constant properties of an object within an
<initialization> within its <entity-decl>.

This would allow such things as

  integer :: Iota(10) = [ ( i, i = 1, size(iota,1) ) ]

6. Alternative syntax
=====================

Same as above.

7. Alternative Edits
====================

[156:30 7.1.12p2] Append to the end of the sentence: ", unless the
specification inquiry appears within an <initialization>."