4.6.5.6 Lists

The mark argument to the IP macro can be employed to present a variety of lists; for instance, you can use a bullet glyph (\[bu]) for unordered lists, a number (or auto-incrementing register) for numbered lists, or a word or phrase for glossary-style or definition lists. If you set the paragraph indentation register PI before calling IP, you can later reorder the items in the list without having to ensure that a width argument remains affixed to the first call.

The following is an example of a bulleted list.

.nr PI 2n
A bulleted list:
.IP \[bu]
lawyers
.IP \[bu]
guns
.IP \[bu]
money

A bulleted list:

• lawyers

• guns

• money

The following is an example of a numbered list.

.nr step 0 1
.nr PI 3n
A numbered list:
.IP \n+[step]
lawyers
.IP \n+[step]
guns
.IP \n+[step]
money

A numbered list:

1. lawyers

2. guns

3. money

Here we have employed the nr request to create a register of our own, ‘step’. We initialized it to zero and assigned it an auto-increment of 1. Each time we use the escape sequence ‘\n+[step]’ (note the plus sign), the formatter applies the increment just before interpolating the register’s value. Preparing the PI register as well enables us to rearrange the list without the tedium of updating macro calls.

The next example illustrates a glossary-style list.

A glossary-style list:
.IP lawyers 0.4i
Two or more attorneys.
.IP guns
Firearms,
preferably large-caliber.
.IP money
Gotta pay for those
lawyers and guns!

A glossary-style list:

lawyers
      Two or more attorneys.

guns  Firearms, preferably large-caliber.

money
      Gotta pay for those lawyers and guns!

In the previous example, observe how the IP macro places the definition on the same line as the term if it has enough space. If this is not what you want, there are a few workarounds we illustrate by modifying the example. First, you can use a br request to force a break after printing the term or label.

.IP guns
.br
Firearms,

Second, you could apply the \p escape sequence to force a break. The space following the escape sequence is important; if you omit it, groff prints the first word of the paragraph text on the same line as the term or label (if it fits) then breaks the line.

.IP guns
\p Firearms,

Finally, you may append a horizontal motion to the mark with the \h escape sequence; using the same amount as the indentation ensures that the mark is too wide for groff to treat it as “fitting” on the same line as the paragraph text.

.IP guns\h'0.4i'
Firearms,

In each case, the result is the same.

A glossary-style list:

lawyers
      Two or more attorneys.

guns
      Firearms, preferably large-caliber.

money
      Gotta pay for those lawyers and guns!