Re: [Groff] on \$0

[Bernd Warken]

On Fri, Jul 12, 2002 at 10:05:40AM +0200, Werner LEMBERG wrote:
> 
> Have a look into trace.tmac.  For example, you could do the following:
> 
>   .rn de de!!
>   .de!! de
>   .  ds namespace \\$1
>   .  de!! \\$1
>   ..
>   .
>   .de test
>   .  ds \\*[namespace]:s xxx
>   ..
>   .
>   .als M test
>   .M
>   .
>   .tm \*[namespace]:s
>     => test:s
>   .tm \*[\*[namespace]:s]
>     => xxx
> 
> IMHO this should be sufficient for your purposes.
> 
This works if you do not call your macros within other macros.  
The following example does not work:

.rn de de!!
.de!! de         
.  ds namespace \\$1
.  de!! \\$1             
..
.
.de child
.  ds \\*[namespace]:s yyy
.  tm c: \\*[namespace]:s 
.  tm c: \\*[\\*[namespace]:s]
..
.de parent
.  ds \\*[namespace]:s xxx
.  child
.  tm p: \\*[namespace]:s 
.  tm p: \\*[\\*[namespace]:s]
..
.parent
.ex

=>c: parent:s 
=>c: yyy
=>p: parent:s 
=>p: yyy


BTW, if you run this with `groff -m trace' you will an unjustified
error message

*** de trace enter: de "child"
0.t:7: fatal error: input stack limit exceeded (probable infinite loop)


########################################################################

Another reason is of aesthetical nature.  I want to avoid ugly 
structures like `\\*[namespace]:s' or `groff:package:container:macro:s'.
Using `\$0:s' is tolerable, while longer expressions make programming a
torture and tend to hide errors.

So if there is a method to enable \$0 this would be a giant step 
towards safe local name spaces.  The problems from overriding local 
names in subsequent macro calls leads to serious bugs that are often
hard to be detected.  I wasted a lot of time on tracking such 
unnecessary bugs.

Bernd Warken