RE: [Groff] funny behaviour of \{

[Ted Harding]

On 08-Mar-00 Werner LEMBERG wrote:
> 
> Try the following and look at stderr:
> 
>   .ab\{This causes a funny error message!
> 
> Is this just pathological behaviour or does it make any sense?
> What happens with UNIX troff while calling this?

If (groff 1.11) I do it as you give it above:

  .ab\{This causes a funny error message!

then I get

  This causes a funny error message!


If I do it with a space after .ab:

  .ab \{This causes a funny error message!

then I get

  \{This causes a funny error message!

In either case I'm not seeing anything that looks pathological:
The error message is clean, and in the first case (since I'm not
using compatibility mode) I guess the "\{" is treated as a separator
or an "opening quote".

In the second case, I get exactly what I expected a priori.

Is the first case the behaviour you got? If so, what seems to be
worrying about it? Or (if different) what did you get?

Interestingly, though, when I do this on a Solaris troff (very ancient,
1987 release) I get the first form of output (without the "\{" ) in
each case.

I expected the second in the second case because, as far as I know,
the use of "\{" and "\}" is mentioned in connection with beginning
and ending conditional input (according to both the 1992 ditroff
manual and the 1976 troff manual), and in no other context; and in
groff also in connection with the ".while" request (which shares
the troff ".if" syntax). So I would not expect it to be treated as a
"grouping" operator outside that context.

However, I tested the latter hypothesis using the code:

  .de temp
  .while \\n[.$] \{ .br
  \\$1
  .shift 1 \}
  ..
  .LP
  .temp \{This causes a funny error message!\}

and got:

  This
  causes
  a
  funny
  error
  message!

(i.e. the \{...\} did NOT group the words into a single argument;
yet both \{ and \} disappeared). This is more like the Solaris
behaviour.

So now I'm feeling a bit confused ...

Ted.


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E-Mail: (Ted Harding) <address@hidden>
Date: 08-Mar-00                                       Time: 23:07:53
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