As I have had occasion to note here before, the traditions of C and
its sequelæ interest me chiefly as illustrations of one or another
pathology.
The PL/I tradition provides better positive guidance. From the
beginning, with the PL/I F
compiler, such a construction as
declare hashvcs entry(character(*) varying, binary fixed(15,0))
returns(binary fixed(15,0)) ;
. . .
declare hashin character(*) varying, hashval binary fixed(15,0) ;
hashval = hashvcs(hashin, 1101b) ;
resulted in the creation of a halfword temporary initialized to have
the binary value 1101b (decimal 13). The address of that temporary,
not that of the (internal/converted) value of the literal 1101b, was
then made available to the entry hashvcs, which was free to mutilate
it without non-local effect.
Today, one can make corresponding distinctions within a function like
hashvcs, as in
hashvcs: procedure(vcs, modulus)
returns(signed binary fixed(15,0))
reorder ;
declare (vcs character(*) varying2,
modulus signed binary fixed(15,0))
nonassignable parameter ;
. . .
return(hashval) ;
end hashvcs ;
C and its sequelæ are and now seem likely to remain toys. They have
achieved all of the portability of assembly language without its
expressive power.
John Gilmore, Ashland, MA 01721 - USA
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