#once #create message
.ND
.tr %$
.EQ
delim $$
.EN
.LP
The next step is to learn how to put big parentheses,
brackets, braces or bars around equations, like this:
.EQ
left | a sup 2 over b sub i right |
.EN

This is done with two new words called "left" and "right".
To put bars around something, you simply say, in the middle
of an equation,
  left |  something  right |
and the job is done.
"something" can indeed be anything, from a single letter
up to some horribly complicated mess.
The bars grow to the right height to cover the
"something", automatically.
To produce the example above, all that was needed was
   .EQ
   left | a sup 2 over b sub i right |
   .EN

For practice, modify file "Example" so it produces output
that looks like this, then type "ready".
.pl 1
#once #create Ref
.LP
.EQ
left |
{a over b ~+~ c over d} over 2
right |
.EN
.pl 1
#once #create Example
.LP
.EQ
replace me
.EN
.pl 1
#
#once neqn Ref | nroff >X1 &
#once neqn message Ref | nroff -T$term %s/tinyms -
#user
neqn Example | nroff >X2
#cmp X1 X2
#log
#next
12.1b 10