Mr Birdsall quotes the list
| Comparison operators
| Logical operators
| NOT (¬) operators
| Relational-expression keywords.
from the JCL manual, and this snippet--apart from the quaint distinction of ¬,
which is a [singulary] logical operator, from & and |, which are [binary]
logical operators--is innocuous.
>From this point forward things are less clear to me. In particular I do at
>all understand the discussion of whether TRUE and FALSE are keywords. Is the
>12 in
IF RC = 12 THEN . . .
a keyword? Or again, is S0C4 in
IF ABEND = S0C4
a keyword? The answer to both of these questions and to a denumerable
infinitiy of other similar ones is no. TRUE and FALSE are the [only] possible
values of a logical expression; S0C4, U4000, and the like are among the
possible values of an ABEND code. They are constants, and as such they may
have syntactic and semantic definitions, but they are not keywords.
More generally, while JCL is certainly an acronym for Job Control Language, JCL
is not a language either in the sense in which Estonian is a language or in the
sense in which FORTRAN or XML is a language. Much of it is ad hoc, and
attempts to formalize it or ask very precise questions about its syntax are
certain to fail.
JCL slip paths like those Mr Birdsall discusses abound; and you exploit them at
your peril: the next z/OS release may omit to support them without a conscious
decision by anyone to yank their support.
Finally, it is not clear to me that constructs of the form
IF <always true construct> THEN
. . .
ELSE
. . .
or
IF <always false construct> THEN
. . .
ELSE
. . .
have legitimate uses since both THEN and ELSE groups may be empty.
What qppear to be under discussion here are questions on the model of Aquinas's
quaestio whether angels in translocating from A to B pass through the
intervening space, which 700 years of often learned discussion have not much
clarified.
John Gilmore Ashland, MA 01721-1817 USA
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