[bug #54537] [PATCH] om.tmac: Add block brackets to avoid a warning about unbalanced .ie

[G. Branden Robinson]

Update of bug #54537 (project groff):

              Item Group:                    None => Incorrect behaviour    

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Follow-up Comment #7:

This was an actual correctness issue with respect to *roff syntax, though
whether it had any discernible impact on mom(7)'s operation, I am not remotely
prepared to opine.

`el` is a request much like any other, and does not "bind" at a lexical level
to its companion `ie` request more tightly than any other request does.  This
means that if an `ie`/`el` pair is governed by another conditional, they
_must_ be braced for correct behavior.  Here's an illustration.


$ cat EXPERIMENTS/block-and-el.roff 
.nr a 1
.nr z 0
.ie \nz \
.  ie \na a is true
.  el     a is false
.el z is false
$ ./build/test-groff -Tutf8 -b -ww EXPERIMENTS/block-and-el.roff | cat -s
troff: backtrace: file 'EXPERIMENTS/block-and-el.roff':6
troff:EXPERIMENTS/block-and-el.roff:6: warning: unbalanced 'el' request
a is false



Another trick you can play with `el` is (nowadays) documented in our Texinfo
manual.


5.20.3 if-else
--------------

 -- Request: .ie cond-expr anything
 -- Request: .el anything
     Use the 'ie' and 'el' requests to write an if-then-else.  The first
     request is the "if" part and the latter is the "else" part.
     Unusually among programming languages, any number of
     non-conditional requests may be interposed between the 'ie' branch
     and the 'el' branch.

          .nr a 0
          .ie \na a is nonzero.
          .nr a +1
          .el a was not positive but is now \na.
              => a was not positive but is now 1.


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