4.3BSD-UWisc/lib/learn/eqn/L12.1b

#print
Bars are not the only characters you can put 
around an equation.
If you say
  left (  thing  right )
you will get large parentheses around "thing".
You can also use [ and ] for large square brackets
and { and } for large braces.

The main problem is that on your terminal there is
no good way for neqn to draw large braces
or brackets or parens.  So neqn replaces all of these
with bars.
Use the right character anyway, though - things do
work properly on the typesetter.  And who knows, some day
neqn may get improved as well.

With the current version of neqn, does the input
  left { a over b right }
produce the same output as
  left [ a over b right ]
Answer yes or no.
#copyin
#user
#uncopyin
#match yes
#log
#next
12.1c 10