On 24/12/16 12:30, Bernd Oppolzer wrote:
Am 24.12.2016 um 12:50 schrieb Mark Morgan Lloyd:
You are mentioning SUCC and PRED with CHAR; that is a very cood example.
It's not so much a good example as a specific sticking point that was
mentioned in earlier discussion on the ML.
These functions are implemented based on the underlying character set;
that means, that SUCC('R') is not 'S' on EBCDIC, because there is a gap
between
'R' and 'S in the EBCDIC codepage (six other characters between 'R' and 'S'
which are not alphabetic).
This is a portability problem which appears at the source code level (!)
and cannot be healed by the compiler. It is the same with the C language,
and the sensible programmer has to deal with this, if he or she wants to
have his or her programs really portable.
At least a-f are consecutive, and it's still possible to switch letter
case with an addition. I've used a tool in the past, written by what I
have to assume was one of the Three Wise Men, which made no assumptions
other than that 0-9 were consecutive: everything else was specified on
the first line of every file.
My problems with the Stanford compiler were different; if the compiler
generates
code which will not run on a platform using a different code page,
because it generates
branch tables when implementing case statements that imply a certain
code page,
Ouch :-(
Regarding ^:
"my" compiler supports different representations for the pointer symbol,
and for other
critical symbols, too:
^ @ -> for the pointer symbol (I use -> most of the time)
[ (. (/ for arrays
{ (* /* for comments ("comment" is supported, too, for historic
reasons)
/* was the form used in the first edition of Wirth's description of
Pascal (might have been before Jensen was there to help out). However
I'd strongly suggest deprecating @ and replacing it with another
digraph, it's used as the address-of operator in Turbo Pascal and its
successors.
--
Mark Morgan Lloyd
markMLl .AT. telemetry.co .DOT. uk
[Opinions above are the author's, not those of his employers or colleagues]
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