topic Re: F$TYPE of space is INTEGER in Operating System - OpenVMS

F$TYPE of space is INTEGER

Lester_Dreckow — Wed, 01 May 2013 00:25:48 GMT

Who would have thought that f$type of a symbol containing a space is considered to be an integer! It looks more like a string. Oh well, I guess we can code around it.

$ s = " "
$ t = f$type(s)
$ show symbol %
S = " "
T = "INTEGER"
$

But the empty string is a string.

$ s = ""
$ t = f$type(s)
$ show symbol %
S = ""
T = "STRING"
$
$ tcpip show version

HP TCP/IP Services for OpenVMS Industry Standard 64 Version V5.6 - ECO 5
on an HP rx3600 (1.59GHz/9.0MB) running OpenVMS V8.3-1H1

Cheers,

Lester

Re: F$TYPE of space is INTEGER

Hein van den Heuvel — Wed, 01 May 2013 02:54:10 GMT

That's a bug/inconsistency....

fwiw,

Hein.

DCL

LEXICON

.. F$TYPE

TSTL R1 ;NULL STRING?
BEQL 10$ ;YES, THEN BRANCH
:

JSB DCL$CNVASCBIN ;CONVERT THE STRING TO DECIMAL

TSTL R0 ; Test return status
BEQL 150$ ;IF SUCCESSFUL, THEN INTEGER

; SYMBOL IS A STRING
10$: MOVAB STRING,R2 ;SETUP RETURN DESCRIPTOR

CONVERT

...DCL$CNVASCBIN:: ; CONVERT IN SPECIFIED RADIX
:

BSBW DCL$TRIM ; TRIM AND UPCASE THE STRING

CLRL-(SP); SAVE ROOM FOR "NUMBER SEEN" FLAG

MOVL R2,R0 ; TEST FOR ZERO LENGTH STRING

BEQL 70$ ; IF IT IS THE NULL STRING-RETURN ZERO

70$:...

BLBC (SP)+,90$ ; IF A NUMBER SEEN, FLAG OK AS IS
MOVL #1,R0 ; IF NO NUMBER SEEN, UNCONDITIONALLY SET TO FAILURE

90$: RSB ; BACK TO THE CALLER

Re: F$TYPE of space is INTEGER

John McL — Thu, 02 May 2013 22:58:55 GMT

Never take even simple claims at face value. I just tested the sequence described here and got different ...

$ s = ""
$ t = f$type(s)
$ sho sym %
S = ""
T = "STRING"
$ tcpip show version

HP TCP/IP Services for OpenVMS Alpha Version V5.6 - ECO 5
on an AlphaServer DS25 running OpenVMS V8.3

The obvious difference is that I'm on Alpha and running 8.3 (nothing), but this code seems so fundamental to VMS you wouldn't think that it would change.

Re: F$TYPE of space is INTEGER

John McL — Thu, 02 May 2013 23:00:56 GMT

Sorry - my mistake.

A single space character does indeed return type "INTEGER", so does a string of two spaces and even a string of about 30 spaces.

Re: F$TYPE of space is INTEGER

John McL — Thu, 02 May 2013 23:07:10 GMT

Further, it looks like an issue with how VMS converts numeric strings into integers.

$ s = "0"
$ t = f$type(s)
$ sho sym t
T = "INTEGER"
$ s = "A"
$ t = f$type(s)
$ sho sym t
T = "STRING"

and here's why I think so ...

$ s = " " ! space character
$ r = 4
$ x = r + s
$ sho sym x
X = 4 Hex = 00000004 Octal = 00000000004

A string that's comprised of a space character, is treated as a 0 when processing integer arithmetic.

Re: F$TYPE of space is INTEGER

abrsvc — Thu, 02 May 2013 23:52:07 GMT

I haven't looked at the code, but I would expect that leading spaces are ignored in most cases when checking for integers and the result would end up being a zero length which is caught as the code already posted shows.

Dan

Re: F$TYPE of space is INTEGER

John Gillings — Mon, 06 May 2013 05:04:55 GMT

Dan,

I agree with Hein. It looks like a bug to me. However, I'd bet that if you report this, VMS engineering will say they can't fix it because folk may be depending on the bug behaviour. The curse of fanatical upwards bug-for-bug compatibility! I've had far more serious bug reports rejected on these grounds.

That said, in this case I think I'd reluctantly agree with them. This is very basic stuff, and the behaviour must have been there a very long time. There is a rather unconvincing argument that it could be considered kind of, sort of correct (but that would apply equally to the null string).

re: John McL> A string that's comprised of a space character, is treated as a 0 when processing integer arithmetic.

Well, all strings have a numeric value, it's just not always obvious what it will be. Most are zero, but not always. For example, here's a good DCL trivia question. How come some of these results are 5?

$ r=4
$ s="A String"
$ x=r+s
$   show sym x
  X = 4   Hex = 00000004  Octal = 00000000004
$ s="This String"
$ x=r+s
$ show sym x
  X = 5   Hex = 00000005  Octal = 00000000005
$ s="Yellow string"
$ x=r+s
$  show sym x
  X = 5   Hex = 00000005  Octal = 00000000005
$ s="New string"
$ x=r+s
$ show sym x
  X = 4   Hex = 00000004  Octal = 00000000004
$ s="Forgotten string"
$ x=r+s
$ show sym x
  X = 4   Hex = 00000004  Octal = 00000000004

Re: F$TYPE of space is INTEGER

Lester_Dreckow — Tue, 07 May 2013 06:21:04 GMT

> DCL trivia question

Good one John :-)

Cheers,

Lester