J3/17-216
To: J3
From: Malcolm Cohen
Subject: Badly worded contradictions
Date: 2017 October 09


1. Introduction

This paper proposes repairing some badly worded and contradictory text.
No technical effect is intended.


2. Generalized integer editing

In paragraph 1 of 13.7.5.2.1 Generalized integer editing, the wording for
the Gw.d and G0.d edit descriptors is contradictory.  It says
  "When used to specify the input/output of integer data, the Gw.d and
   Gw.d Ee edit descriptors follow the rules for the Iw edit descriptor
   (13.7.2.2), except that w shall not be zero."
Note that this is a hard requirement that for integer i/o, in an edit
descriptor of the form Gw.d, w is not permitted to be zero.  This directly
contradicts the Introduction which states there is a new feature:
  "The G0.d edit descriptor can be used for list items of type Integer,
    Logical, and Character."
as well as contradicting the second sentence of this paragraph,
  "When used to specify the output of integer data, the G0 and G0.d edit
   descriptors follow the rules for the I0 edit descriptor."
because the second sentence implies that G0.d is valid.

Also, note that the meaning of the second sentence, as in "what edit
descriptor" this refers to, is precisely the same as the first: the Iw
edit descriptor.

Finally, there is no such edit descriptor as G0 or G0.d.  These are merely
the Gw and Gw.d edit descriptors (that's what they are in the syntax!).
In the case of G0/Gw, G0 is reasonable because the w in Gw is constrained
by C1307 to be zero.

It is clear that this unfortunate phrasing is merely a botched attempt to
add the feature described in the Introduction.  An edit is included to
repair this.

Post-finally, there is no statement here of the semantics of G0 for input,
but this is mentioned in 13.5.7.1 Overview (it is not allowed).  As the
paragraph already redundantly repeats the requirement for w/=0 on input,
there is a good case for either NOT repeating that requirement (simplifies
the paragraph significantly), or for repeating the requirement against
Gw (where w is required to be zero).

Note that the edit basically rewrites the paragraph into a much simpler
form, because even after fixing the contradictions, for input,
  "follow the rules for the Iw edit descriptor (...) except that w shall
   not be zero"
is nonsense because the Iw edit descriptor *does* require w to be nonzero
for input editing!


3. Generalized logical and character editing

For logical editing, the text states both that Gw.d follows the rules for
Lw, and for G0.d follows the rules for L1.  The former is wrong when w is
equal to zero (there is no L0 edit descriptor), quite apart from
contradicting the second sentence.

Character editing has the same flaw as logical editing.


4. Edits to 17-007r2 (N2137)

[281:17-19] 13.7.5.2.1 Generalized integer editing, p1,
  Replace the whole paragraph with
    "When used to specify the input/output of integer data, the Gw, Gw.d,
     and Gw.d Ee edit descriptors follow the rules for the Iw edit
     descriptor (13.7.2.2)."
OPTIONAL REDUNDANT APPENDAGE:
    "Note that w cannot be zero for input editing (13.5.7.1).".

[282:3] 13.7.5.3 Generalized logical editing, p1,
  After "Gw.d Ee edit descriptors" insert "with nonzero <w>",
  Making the whole paragraph read:
    "When used to specify the input/output of logical data, the Gw.d and
     Gw.d Ee edit descriptors with nonzero w follow the rules for the Lw
     edit descriptor (13.7.3). When used to specify the output of logical
     data, the G0 and G0.d edit descriptors follow the rules for the L1
     edit descriptor."

[282:7] 13.7.5.4 Generalized character editing, p1,
  After "Gw.d Ee edit descriptors" insert "with nonzero <w>",
  Making the whole paragraph read:
    "When used to specify the input/output of character data, the Gw.d and
     Gw.d Ee edit descriptors with nonzero w follow the rules for the Aw
     edit descriptor (13.7.4). When used to specify the output of
     character data, the G0 and G0.d edit descriptors follow the rules for
     the A edit descriptor with no field width."

===END===