To:        J3                                                J3/15-172
Subject:   MERGE_PTR intrinsic function
From:      Van Snyder
Reference: 15-007r1
Date: 2015 June 07

1. Proposal
===========

Provide a MERGE_PTR intrinsic function that returns a pointer associated
with the first argument, or its target if it is a pointer and is
associated, if the third argument is true, or the second argument, or
its target if it is a pointer and is associated, if the third argument
is false.

2. Draft Edits
==============

[328 Table 13.1] Insert a row in Table 13.1:

"MERGE_PTR   (TSOURCE, FSOURCE, MASK)       T   Pointer selection
"

[381:6+ 13.8.122+] Insert a subclause

"
13.8.121a MERGE_PTR (TSOURCE, FSOURCE, MASK)

<<Description.>> Pointer selection.

<<Class.>> Transformational function.

<<Arguments.>>

TSOURCE  may be of any type, kind and rank.  It shall be a pointer,
         or have the TARGET attribute.

FSOURCE  shall be of the same declared type, kind, and rank as TSOURCE.
         It shall be a pointer, or have the TARGET attribute.

MASK     shall be a scalar of type logical.

<<Result characteristics.>> A pointer of the same declared type, kind,
and rank as TSOURCE.  The result is polymorphic if and only if either
TSOURCE or FSOURCE is polymorphic.

<<Result value.>>

Case (i):  If MASK is true, the result is a pointer of the same dynamic
           type, kind and rank as TSOURCE.  If TSOURCE is not a pointer,
           the result is associated with TSOURCE and has the same
           shape.  If TSOURCE is a pointer, the result has the same
           pointer association status as TSOURCE, and if TSOURCE is
           associated the result is associated with the same target and
           has the same shape.

Case (ii): If MASK is false, the result is a pointer of the same dynamic
           type, kind and rank as FSOURCE.  If FSOURCE is not a pointer,
           the result is associated with FSOURCE and has the same
           shape.  If FSOURCE is a pointer, the result has the same
           pointer association status as FSOURCE, and if FSOURCE is
           associated the result is associated with the same target and
           has the same shape.

<<Examples.>>  If X is a pointer and Y is not a pointer, the result of
MERGE_PTR ( X, Y, .TRUE. ) is associated with X, and the result of
MERGE_PTR ( X, Y, .FALSE. ) is a pointer having the same pointer
association status as Y.  If MERGE_PTR ( X, NULL(X), COND ) is an actual
argument corresponding to an optional nonpointer dummy argument and X is
not a pointer, the dummy argument is present and associated with X if
COND is true and absent if COND is false. "