J3/06-141

Date:    2006/02/16
To:      J3
From:    Malcolm Cohen
Subject: Simplified KIND selection
References: Item J3-030, J3/04-240, J3/04-407r1, WG5/N1649.

INTRODUCTION

  This paper proposes specifications, syntax and edits for simplified kind
  selection.

REQUIREMENTS

  The requirement is to provide a simplified means to select the most commonly
  desired real and integer kinds.

SPECIFICATIONS

  The standard will specify the names of several named constants in the
  ISO_FORTRAN_ENV intrinsic module. These named constants will have kind values
  for the representations described below.

  Named constants provided will be for the kinds of integers whose storage
  sizes are exactly 8, 16, 32, and 64 bits, and for the kinds of reals whose
  storage sizes are exactly 32, 64, and 128 bits.

  If the processor supports more than one representation with the specified
  size, it is processor-dependent which of those representations the named
  constant corresponds to.

  If the processsor does not support a particular representation, the value of
  the corresponding named constant will be one of two negative values specified
  by the standard. If the processor does not support a representation with the
  exact size requested or with any larger size, the value shall be -1. If the
  processor does not support a representation with the exact size requested,
  but does support a representation with a larger size, the value shall be -2.

  This proposal does not require the compiler to support any particular
  kind.  Nor does this proposal specify the kind values, which remain
  processor-dependent.

SYNTAX

  The names shall be:
    INT8, INT16, INT32, INT64, REAL32, REAL64 and REAL128.

EDITS

[360:17+] Insert new subclause
  "13.8.2.4a INT8, INT16, INT32, and INT64

   The values of these default integer scalar named constants shall be those of
   the kind type parameters that specify an INTEGER type whose storage size
   expressed in bits is 8, 16, 32, and 64 respectively.  If, for any of these
   constants, the processor supports more than one kind of that size, it is
   processor-dependent which kind value is provided.  If the processor supports
   no kind of a particular size, that constant shall be -2 if the processor
   supports kinds of a larger size and -1 otherwise."

[360:33+] Insert new subclause
  "13.8.2.8a REAL32, REAL64, and REAL128

   The values of these default integer scalar named constants shall be those of
   the kind type parameters that specify a REAL type whose storage size
   expressed in bits is 32, 64, and 128 respectively.  If, for any of these
   constants, the processor supports more than one kind of that size, it is
   processor-dependent which kind value is provided.  If the processor supports
   no kind of a particular size, that constant shall be -2 if the processor
   supports kinds of a larger size and -1 otherwise."

===END===