Paul Gilmartin <[EMAIL PROTECTED]>, with whom I often diisagee not
just intellectually but viscerally too, judges that nulled-out JCL defaults
should be supported; and he has found an IBM JCL-statement option that does
so.
Tastes differ, sometimes radically. In my own HLASM macro definiitions I
treat overriding a default value without replacement as a grievous error.
For, say,
| macro
| example &parm=gubbins, . . .
| . . .
| mend
the macro instruction
| example parm =, . . .
triggers execution of the statements
|&in setb (t'&parm ne 'O') --value supplied?
| aif (&in),parm_in --if so, examine it
|&abort setb 1 --no, set quit switch
| mnote &el,'&mnpfx.07i. A value of the parm= keyword parameter*
| must be but has not been supplied. Moreover, this error is
an*
| aggravated one. The default value parm=gubbins has been o*
| verridden without replacement.'
| ago .after_parm
|.parm_in anop
| . . .
As this small example illustrates, macros can be written in different ways;
and JCL support for parameter values can differ too. (Failure to understand
that the original model for the syntax of JCL was that of the HLASM macro
language is the root of much trouble.)
Certain facilities may thus support the dubious practice of treating
. . . ,parm=, . . .
and
. . . ,parm=<default value>, . . .
as equivalent; but, I think fortunately, there is no mechanism currently
avaiable for ensuring that all of them do so.
John Gilmore
Ashland, MA 01721-1817
USA
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