SUN pascal

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2 total messages Started by Philip Budne Mon, 05 May 1986 22:39

#291

Author: Philip Budne
Date: Mon, 05 May 1986 22:39

46 lines
1291 bytes

Transposrting some pascal code from a BSD4.2 system to a SUN3.0 system
I ran into some range check problems.  The first would appear to be
an actual error (in the ISO defintion), and the other a SUN pascal
bug.

-----
program q(input,output);

var
	a : 0 .. 100;
	i : integer;

begin
	i := 0;
	for a := 0 to i-1 do
		writeln(output, a);
end.
-----
program z;

var
	c : char;
	i : -128 .. 127;

begin
	i := 10;
	c := chr( i );
end.
-----

For more entertainment I tried the same programs under TOPS-20/Rutgers
and VMS v4 pascal:

	q	z
TOPS	err	ok
SUN	err	err
BSD	ok	ok
VMS	ok	ok


The range violation in Z clearly a SUN bug, but Q would
appear to be implementation dependant, it all depends
on when you perform the range check (and if you check the
loop limits before you start).

Phil Budne / Boston University / Distributed Systems

Re: SUN pascal

#292

Author: Charles Hedrick
Date: Tue, 06 May 1986 02:27

26 lines
1654 bytes

	a : 0 .. 100;
	i := 0;
	for a := 0 to i-1
The standard says that the lower and upper bounds must be assignment
compatible with the control variable if the statement is executed.
In this case, the loop is from 0 to -1, so the loop is not executed.
Thus the compatibility test is not to be enforced.  This code is
therefor legal.

	i : -128 .. 127;
	i := 10;
	c := chr (i);
The standard says that the argument to chr must be compatible with
integer, which it is.  The actual value passed must translate to a
legal character, or it is an error.  It is up to the implementation as
to what characters are legal.  At first glance, I would say that 10 is
a legal character.  The only excuse I can think of is that 10 is
really a linefeed.  One might take the view that linefeed is not a
legal character in a Unix implementation of Pascal, since it can never
be read.  Read will treat it as an end of line marker and turn it into
a blank.  I suggest trying the same program with a value of i that is
some printable character.

Incidentally, your table showed that TOPS-20 Pascal rejects the first
example.  That was a bug, and was fixed on 29-Jan-84.

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