J3/15-161
To:        J3
From:      Van Snyder
Subject:   Interp: assign to deferred-length coindexed character
Date: 2015 June 06

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NUMBER: F08/nnnn
TITLE: Assign to deferred-length coindexed character variable
KEYWORDS: Cobounds, type declaration
DEFECT TYPE: Erratum
STATUS: J3 consideration in progress

QUESTION:

Consider the program:

  character(:), allocatable :: C[*]
  allocate ( character(42) :: C )
  c = 'stuff'
  end

Is the assignment permitted?

ANSWER:

7.2.1.2p2 is poorly written.  Taking only the introductory sentence
and the third list item, one has the nongrammatical nonsense "If
<variable> is a coindexed object, the variable each deferred length
type parameter shall have the same value as the corresponding type
parameter of <expr>."

Nonetheess, one can penetrate its intent, which is that if a variable
is a coindexed object, each deferred length type parameter of the
variable shall have the same value as the corresponding length type
parameter of the expression.  In the question, the length type
parameter values are 42 and 5.

Therefore the assignment is prohibited.

7.2.1.2p1(8) clearly contemplates that the requirement does not apply
to character variables that are not coindexed.  Further, 7.2.1.3p10
explains how character assignment works when the length type parameter
values differ.  7.2.1.3p10 does not make any distinction between
coindexed variables and variables that are not coindexed.

It was intended that the assignment be allowed, and that assignment to
character variables that are coindexed work the same way as assignment
to character variables that are not coindexed.  Edits are provided to
correct this mistake.

EDITS:

Replace 7.2.1.2p2 with the following paragraph:

"If <variable> is a coindexed object then

  o the variable shall not be polymorphic,
  o the variable shall not have an allocatable ultimate component, and
  o if the variable is of derived type, each of its deferred length
    type parameters shall have the same value as the corresponding
    type parameter of <expr>.
"

SUBMITTED BY: Van Snyder

HISTORY: 15-xxx    m207  F08/nnnn submitted

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