In response to my strictures against strong typing Clark Morris wrote:
As someone who has made great use of the COBOL REDEFINES option, I
don't think that strong typing would necessarily be an impediment to
writing operating system code. I wanted optional flagging because of
people with your point of view. Coming from a COBOL background where
changes in the data definition are automatically accommodated, I
believe that flagging can reduce inadvertent errors. Also making the
operation match the data definition can reduce confusion for the
person who inherits the assembler code.
I am not sure just how to react to this, except to acknowledge that we are
all creatures of our experience, which is often very different and in
consequence of which we often see the world very differently too.
There are, I suppose, two polar programming postures. The first is
move-orient[at]ed, compile-time bound, and synchronous. The second is list-
and pointer-orient[at]ed, execution-time bound, and asychronous.
I have often marvelled at the---in my view entirely misplaced or, better,
mistimed---radical ingenuity embodied in COBOL REDEFINES and analogous
constructs in other SLPLs. (Both C and PL/I can be and now often are
written as a species of COBOL with semicolons.)
COBOL now supports what it calls address modifications and the rest of us
call substring operations, and the availability of execution-time substring
operations entirely eliminates the need for compile-time REDEFINES
operations. Predictably, however, REDEFINES continue to be used heavily;
and the use of address modification is still exiguous.
At my advanced age I have lost any messianic zeal I may once have had to
convert experienced programmers who think in and write move-orient[at]ed
idioms to the use of list- and pointer-orient[at]ed ones instead, not least
because such conversions are anyway all but impossible; but I do find
attempts to introduce COBOL-like assembly-time constraints into the HLASM
very disagreeable.
John Gilmore
Ashland, MA 01721-1817
USA
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