@Section
   @Title { Lists }
   @Tag { lists }
@Begin
@PP
The @Code "@IndentedList" symbol introduces a sequence of items to be
indentedlist. @Index @Code "@IndentedList"
il. @Index @Code "@IL"
lists. @Index { lists }
made into a displayed list:
@ID @OneRow @Code @Verbatim {
preceding text
@IndentedList
@ListItem @I Emma
@ListItem @I { Mansfield Park }
@EndList
following text
}
After the initial @Code "@IndentedList" symbol, each item is introduced by
list.item. @Index @Code "@ListItem"
li. @Index @Code "@LI"
{@Code "@ListItem"}, and the list ends with {@Code "@EndList"}.  The
end.list. @Index @Code "@EndList"
el. @Index @Code "@EL"
result here is
@ID @OneRow {
preceding text
@IndentedList
@ListItem @I Emma
@ListItem @I { Mansfield Park }
@EndList
following text
}
with space inserted automatically before, between, and after
the items.
@PP
As the example shows, the @Code "@IndentedList" symbol causes the items to be
indented.  Also available are {@Code "@LeftList"},
leftlist. @Index @Code "@LeftList"
ll. @Index @Code "@LL"
{@Code "@QuotedList"}, {@Code "@CentredList"}, and {@Code "@CenteredList"},
quotedlist. @Index @Code "@QuotedList"
ql. @Index @Code "@QL"
centredlist. @Index @Code "@CentredList"
centeredlist. @Index @Code "@CenteredList"
cl. @Index @Code "@CL"
which format the items like the corresponding display symbols do.
Other list symbols generate a @I label for each item.  For example,
@Code "@NumberedList" causes the items to be numbered:
numberedlist. @Index @Code "@NumberedList"
nl. @Index @Code "@NL"
@ID @OneRow @Code @Verbatim {
@Heading { Quiz }
@NumberedList
@ListItem { Which American statesman owned a two-storey clock? }
@ListItem { Which Yankee commander from the Civil War cut a
swathe of destruction through the State of Georgia? }
@EndList
}
has result
@ID @OneRow {
@Heading { Quiz }
@NumberedList
@ListItem { Which American statesman owned a two-storey clock? }
@ListItem { Which Yankee commander from the Civil War cut a
swathe of destruction through the State of Georgia? }
@RawEndList
}
The generated labels are added at the left margin.
Here is the full set
of label-generating list symbols, showing the first label produced by each:
parennumberedlist. @Index @Code "@ParenNumberedList"
pnl. @Index @Code "@PNL"
romanlist. @Index @Code "@RomanList"
rl. @Index @Code "@RL"
parenromanlist. @Index @Code "@ParenRomanList"
prl. @Index @Code "@PRL"
ucromanlist. @Index @Code "@UCRomanList"
ucrl. @Index @Code "@UCRL"
parenucromanlist. @Index @Code "@ParenUCRomanList"
pucrl. @Index @Code "@PUCRL"
alphalist. @Index @Code "@AlphaList"
al. @Index @Code "@AL"
parenalphalist. @Index @Code "@ParenAlphaList"
pal. @Index @Code "@PAL"
ucalphalist. @Index @Code "@UCAlphaList"
ucal. @Index @Code "@UCAL"
parenucalphalist. @Index @Code "@ParenUCAlphaList"
pucal. @Index @Code "@PUCAL"
bulletlist. @Index @Code "@BulletList"
bl. @Index @Code "@BL"
starlist. @Index @Code "@StarList"
sl. @Index @Code "@SL"
dashlist. @Index @Code "@DashList"
dl. @Index @Code "@DL"
@ID @Tab
    @Fmta { @Col @CC A ! @Col @Code B ! @Col ! @Col @CC C ! @Col @Code D }
{
@Rowa
    A { 1. }
    B { "@NumberedList" }
    C { (1) }
    D { "@ParenNumberedList" }
@Rowa
    A { i. }
    B { "@RomanList" }
    C { (i) }
    D { "@ParenRomanList" }
@Rowa
    A { I. }
    B { "@UCRomanList" }
    C { (I) }
    D { "@ParenUCRomanList" }
@Rowa
    A { a. }
    B { "@AlphaList" }
    C { (a) }
    D { "@ParenAlphaList" }
@Rowa
    A { A. }
    B { "@UCAlphaList" }
    C { (A) }
    D { "@ParenUCAlphaList" }
@Rowa
    A { @Bullet }
    B { "@BulletList" }
@Rowa
    A { @Star }
    B { "@StarList" }
@Rowa
    A { -- }
    B { "@DashList" }
}
roman @Index { Roman numerals }
The Roman numerals end at cc (200), but ordinary decimal numbers have
no limit.  The labels produced by the four alphabetical list symbols are
determined by the current language; in English they start at @Code "a"
and end at {@Code "z"}.
@PP
You may also supply your own labels using the @Code "@TaggedList"
taggedlist @Index @Code "@TaggedList"
tl. @Index @Code "@TL"
symbol.  Each item is introduced by @Code "@TagItem" instead of
tagitem. @Index @Code "@TagItem"
ti. @Index @Code "@TI"
{@Code "@ListItem"}.  Since such labels tend to be quite wide,
there are @Code "@WideTaggedList" and @Code "@VeryWideTaggedList" symbols
widezzztaggedlist @Index @Code "@WideTaggedList"
wtl. @Index @Code "@WTL"
verywidetaggedlist @Index @Code "@VeryWideTaggedList"
vwtl. @Index @Code "@VWTL"
which leave extra space for them:
@ID @OneRow @Code @Verbatim {
@WideTaggedList
@TagItem { 9 a.m. } { Breakfast in the Ipamena Lounge,
served with Irish coffee and fresh croissants. }
@TagItem { 10 a.m. } { Prof. A. Smith
speaks on `The Wealth of Nations.' }
@EndList
}
Each @Code "@TagItem" symbol is followed by the desired label between
braces, and then the item proper.  The label may be empty, but still its
enclosing braces must be there.  The result here is
@ID @OneRow {
@RawWideTaggedList
@TagItem { 9 a.m. } { Breakfast in
the Ipamena Lounge, served with
Irish coffee and fresh croissants. }
@TagItem { 10 a.m. } { Prof. A. Smith
speaks on `The Wealth of Nations.' }
@RawEndList
}
An alternative way to accommodate wide labels is the `drop item,'
drop.item @Index { drop items }
which looks like this:
@ID @OneRow {
@RawTaggedList
@DTI { 10 a.m. } { Prof. A. Smith speaks on `The Wealth of Nations.' }
@RawEndList
}
Individual items are dropped in this way by using @Code "@DropTagItem"
drop.tag.item @Index @Code "@DropTagItem"
dti. @Index @Code "@DTI"
instead of {@Code "@TagItem"}.  There is also a @Code "@DropListItem"
drop.list.item @Index @Code "@DropListItem"
dli. @Index @Code "@DLI"
symbol corresponding to {@Code "@ListItem"}, but it is very rarely
needed.  Lout is not able to decide for itself whether a label is wide
enough to require a drop item.  Lout will refuse to skip to the next
column or page between a drop tag and its item, preferring instead
to move the drop tag to the next column or page.
@PP
Each list has a `raw' version which omits the preceding space, and
raw.lists @Index { raw lists }
raw.list. @Index @Code "@RawList"
raw.end.list. @Index @Code "@RawEndList"
@Code "@EndList" has a raw version which omits the following
space.  These are mainly used when an item is itself a list:
@ID @OneRow @Code @Verbatim {
@ParenNumberedList
@ListItem {
   @RawParenRomanList
   @ListItem { MV Nominees,
hereinafter called the vendor, ... }
   @RawEndList
}
@EndList
}
produces
@ID @OneRow {
@RawParenNumberedList
@ListItem {
   @RawParenRomanList
   @ListItem { MV Nominees,
hereinafter called the vendor, ... }
   @RawEndList
}
@RawEndList
}
If @Code "@ParenRomanList" had been used instead of
{@Code "@RawParenRomanList"}, (1) and (i) would have appeared on
different lines; or if @Code "@EndList" had been used instead of
{@Code "@RawEndList"}, there would have been too much space following
the list.
@PP
A list item may come out partly on one page or column and partly on
the next, if it has places where it obviously can be broken in two.  For
example, a list item which is an ordinary paragraph of text might be
broken in two between any two lines.  To force a list item to keep
together on one page or column, use the @Code "@OneRow" symbol like
this:  @Code "@ListItem @OneRow { ... }".
@PP
Occasionally it is desirable to start a new page or column between
two list items.  This cannot be done by inserting @Code "@NP"
between them, because the space between two list items is a kind
of no-man's land where nothing is allowed to be.  Instead, the
@Code "@ListNewPage" symbol is used:  it is permitted only between
two list items, and its effect is to make the following list item
appear at the top of the next page or column.  It may be used within
any kind of list.
@PP
Another special list item is {@Code "@ListInterruptItem"}.  This
prints its content without any numbering or formatting:
@ID @OneRow @Code @Verbatim {
@NumberedList
@ListItem { This is the first list item. }
@ListInterruptItem { This is an interruption to the list. }
@ListItem { This is the second list item. }
@EndList
}
produces
@ID @OneRow {
@RawNumberedList
@ListItem { This is the first list item. }
@ListInterruptItem { This is an interruption to the list. }
@ListItem { This is the second list item. }
@RawEndList
}
Although @Code "@ListInterruptItem" is written like a list item, the
result appears to be an interruption to the list.  It may be used
in any kind of list.
@PP
Yet another kind of list item symbol is
paragraph.item. @Index @Code "@ParagraphItem"
pi. @Index @Code "@PI"
{@Code "@ParagraphItem"}, which introduces a list item
whose labels are integrated into a paragraph:
@ID @OneRow @Code @Verbatim {
@Heading { Extract from GNU General Public License }
@LeftList
@ParagraphItem {
You may copy and distribute verbatim copies of the Program's
source code as you receive it, in any medium, provided that you
conspicuously and appropriately publish on each copy an appropriate
copyright notice and disclaimer of warranty ...
}
@ParagraphItem {
You may modify your copy or copies of the Program or any portion
of it, thus forming a work based on the Program, and copy and
distribute such modifications or work under the terms of Section 1
above, provided that you ...
}
@EndList
}
has result
@ID @OneRow {
@Heading { Extract from GNU General Public License }
@LeftList
@ParagraphItem {
You may copy and distribute verbatim copies of the Program's
source code as you receive it, in any medium, provided that you
conspicuously and appropriately publish on each copy an appropriate
copyright notice and disclaimer of warranty ...
}
@ParagraphItem {
You may modify your copy or copies of the Program or any portion
of it, thus forming a work based on the Program, and copy and
distribute such modifications or work under the terms of Section 1
above, provided that you ...
}
@RawEndList
}
Since the numbers are part of the item, the kind of list to use
is just {@Code "@LeftList"} rather than {@Code "@NumberedList"}.
It would be better if @Code "@ListItem" could be used, but problems
behind the scenes prevent this.  @Code "@ParagraphItem" has a
@Code "style" option that works much like the @Code "style" option
of {@Code "@List"} described just below.
@PP
Another useful variation is the @I { multi-column list }, in
which the items are spread over several columns within the
current column.  Any kind of list may be converted into a
multi-column list.  For example, here is how to get a
multi-column bullet list:
@ID @OneRow @Code @Verbatim {
@BulletList
    colnum { 3 }
    colgap { 1.0c }
    colheight { 5.0c }
}
followed by the list items and @Code "@EndList" as usual.  This
list will appear spread over three columns, with the items placed
down the first column, then down the second, and so on.  The columns
will have equal width, as wide as possible given that they are
separated from each other by the gap given by {@Code "colgap"}.
Ideally, one would want the columns to have equal height, just
enough to hold all the items; but since Lout is not clever enough
to do this, you must specify a fixed height for each column,
using the @Code "colheight" option; and this height must be small
enough to allow the entire list to fit onto one page, since it is
effectively an unbreakable display.
@PP
The value of @Code "colnum" must be either 1, 2, 3, 4, or 5.  If
it is 1 (the default value), @Code "colgap" and @Code "colheight"
are not used and the result is an ordinary list.  The value of
@Code "colgap" and @Code "colheight" may be any width; the default
values are those shown above.  All the features available for
ordinary lists and list items work in the usual way with
multi-column lists:  one may keep a list item in one column by
enclosing it in {@Code "@OneRow"}, cause a break to the next
column using {@Code "@ListNewPage"}, and so on.  If there is not
enough space in the columns to hold all the items (a real possibility
since their height is fixed), any excess is dropped, sometimes with
and sometimes without a confusing error message.
@PP
Every symbol introduced in this section has an abbreviated form
consisting of @Code "@" followed by its capital letters only.  For
example, @Code "@RawNumberedList" abbreviates to {@Code "@RNL"},
and @Code "@ListItem" to {@Code "@LI"}.  The sole exception is
{@Code "@RawList"}, which has no abbreviation because @Code "@RL"
is the abbreviation for {@Code "@RomanList"}.
@PP
list.symbol.options @Index { list symbol options }
Expert users will be interested to learn that all of the list symbols
described in this section are derived from the two basic ones,
@Code "@List" and {@Code "@RawList"}, merely by setting options.  Here
list. @Index @Code "@List"
l. @Index @Code "@L"
are all the options, together with their default values:
@ID @OneRow @Code @Verbatim {
@List
    type { num }
    style { num }
    labelwidth { 2f }
    labelright { No }
    labelrightgap { 2s }
    indent { 0c }
    rightindent { 0c }
    gap { 1v }
    start { 1 }
    font { }
    break { }
    colnum { 1 }
    colgap { 1.0c }
    colheight { 5.0c }
}
These options may be used with all of the list and raw list symbols,
except that some combinations don't make sense, for example @Code "indent"
with {@Code "@CentredList"} or @Code "style" with {@Code "@BulletList"},
since the list symbol has clearly already set the option.
@PP
The @Code "type" option determines the type of numbering (Arabic, Roman,
etc.) and is not intended for ordinary use, since there are distinct
symbols for each type, as we have seen.  The @Code "style" option
determines the format of the label, any @Code "num" symbol within it
being replaced by the number (in Arabic, Roman, etc. as determined by the
@Code "type" option) of the item.  For example, @Code "@ParenNumberedList"
is just
@ID @OneRow @Code @Verbatim {
@List
    style { (num) }
}
and @Code "@BulletList" is just
@ID @OneRow @Code @Verbatim {
@List
    style { @Bullet }
}
with @Code "num" not mentioned since no number is wanted.  The
@Code "@TaggedList" symbol and its variants also have the
@Code "style" option; in their case, the @Code "num" symbol within
it must be mentioned exactly once, and its value is set to produce
the label supplied by the author.
@PP
The @Code "labelwidth" option determines the width set aside for the labels;
this is where @Code "@WideTaggedList" and @Code "@VeryWideTaggedList" differ
from {@Code "@TaggedList"}.  If @Code "labelright" is {@Code "Yes"}, it
means that the label is to appear right-justified in this width, apart from
a width @Code "labelrightgap" to the right of it to separate it from the
content of the list item.  The default value of {@Code "labelrightgap"},
{@Code "2s"}, is the width of two spaces.  If @Code "labelright" is
{@Code No}, @Code "labelrightgap" is not used.
@PP
The @Code "indent" and @Code "rightindent"
options determine the space left blank at the left and right margins.
The value given to these options may be any length, for example
@Code "0.5i" (half an inch), or @Code "0.5f" (half the current font
size).  Section {@NumberOf objects} describes lengths in general.  There
are also three useful symbols denoting lengths:  @Code "@DisplayIndent"
is the amount by which indented and quoted displays are indented;
@Code "@WideIndent" and @Code "@VeryWideIndent" are the indents used by
@Code "@WideTaggedList" and {@Code "@VeryWideTaggedList"}.  Using these
symbols helps to keep documents consistent.
@PP
The @Code "gap" option determines the vertical space inserted between
items.  Once again this must be a length, although since it is
vertical rather than horizontal, somewhat different kinds of lengths
are appropriate:  @Code "1.5v" for 1.5 times the current vertical space
between lines, or the default value, {@Code "@DisplayGap"}, which produces
the amount of vertical space used before and after displays.  Owing to
problems behind the scenes, there is no list option for the space before or after
the list as a whole.  To change this space in one list, use a raw list and
insert your own paragraph symbols; to change it in every list there is a
setup file option, described below.
@PP
The @Code "start" option is the number assigned to the first
item.  It must be decimal:
@ID @OneRow @Code @Verbatim {
@ParenRomanList
    start { 25 }
}
looks strange, but it is the correct way to number the first
item (xxv).
@PP
The @Code "font" option defines a font (or any value suited for
the @Code "@Font" symbol) which is to be applied to each item
(but not the labels).  For example, you might be bothered by
the fact that a list item whose last line has no descenders in
its letters is closer to the next list item, producing a slightly
irregular appearance.  One way to solve this problem is
@ID @OneRow @Code @Verbatim {
@NumberedList
    font { strut }
}
since the value @Code "strut" given to the @Code "@Font" symbol
causes it to insert an invisible vertical strut into every word under
the influence of that symbol.  For more information, including
another way to insert struts, consult Section {@NumberOf precise}.
@PP
The @Code "break" option defines a break style (suitable for the
@Code "@Break" symbol) which is to be applied to each item.  If
you wanted each item in a ragged style, for example, you could
just write
@ID @OneRow @Code @Verbatim {
@NumberedList
    break { ragged }
}
rather than laboriously enclosing each item in @Code "ragged @Break".
@PP
The last three options, {@Code "colnum"}, {@Code "colgap"}, and
{@Code "colheight"} work together to produce multi-column lists,
as explained earlier.  When the default value of @Code "colnum"
is used (i.e. 1), {@Code "colgap"} and {@Code "colheight"} are
ignored and the result is an ordinary list.
@PP
Here is a larger example of these options in action.  Setting both
@Code "indent" and @Code "rightindent" to @Code "@DisplayIndent"
produces an effect similar to {@Code "@QuotedDisplay"}:
@ID @OneRow @Code @Verbatim {
preceding text
@List
    style { @I {Item num}: }
    indent { @DisplayIndent }
    rightindent { @DisplayIndent }
    labelwidth { @WideIndent }
    start { 10 }
@ListItem { The vendor ... in the case of accident.  }
@ListItem { The vendor ... adjacent to the facility. }
@EndList
following text
}
The result is
@ID @OneRow {
preceding text
@List
    style { @I {Item num}: }
    indent { @DisplayIndent }
    rightindent { @DisplayIndent }
    labelwidth { @WideIndent }
    start { 10 }
@ListItem {
The vendor will not be liable for any injury caused by the escape of
radiation or radioactive materials from the facility, nor for the
costs of repair of any property damaged by nuclear blast or fallout
in the case of accident.
}
@ListItem {
The vendor will not be liable for any injury caused by radioactive
materials being transported to or from the facility, nor for injury
caused by radioactive materials stored adjacent to the facility.
}
@EndList
following text
}
You can change the @I default values of the {@Code "labelwidth"},
{@Code "labelright"}, {@Code "labelrightgap"}, {@Code "indent"},
{@Code "rightindent"}, {@Code "gap"}, and {@Code "break"} options, by
setting options called {@Code "@ListLabelWidth"}, {@Code "@ListLabelRight"},
{@Code "@ListLabelRightGap"}, {@Code "@ListIndent"},
{@Code "@ListRightIndent"}, {@Code "@ListGap"}, and
{@Code "@ListBreak"} options in the setup file (Section {@NumberOf setup}).
These default values will then apply to every list in the document unless
overridden by an option, just like the usual default values.  The setup
file also has a {@Code "@ListOuterGap"} option which determines the gap
before the first and after the last list item in non-raw lists.
@End @Section