<List>
<Mark>
<Index Key='Autocompleter'><C>Autocompleter</C></Index>
<C>Autocompleter</C>
</Mark>
<Item>
Set how names are filtered during tab-autocomplete, this can be:
<C>"default"</C>: case-sensitive matching. <C>"case-insensitive"</C>:
case-insensitive matching, or a record with two components named <C>filter</C>
and <C>completer</C>, which are both functions which take two arguments.
<C>filter</C> takes a list of names and a partial identifier and returns all
the members of <C>names</C> which are a valid extension of the partial
identifier. <C>completer</C> takes a list of names and a partial identifier
and returns the partial identifier as extended as possible (it may also change
the identifier, for example to correct the case, or spelling mistakes), or
returns <K>fail</K> to leave the existing partial identifier.
<P/>
This preference is ignored if &GAP; was not compiled with readline support.

<P/>

Default: <C>"default"</C>.
</Item>
<Mark>
<Index Key='Editor'><C>Editor</C></Index>
<Index Key='EditorOptions'><C>EditorOptions</C></Index>
<C>Editor</C>,
<C>EditorOptions</C>
</Mark>
<Item>
Determines the editor and options (used by &GAP;'s <Ref Func="Edit"/>
command). Under macOS, the value <C>"open"</C> for <C>Editor</C> will work.
For further options, see the &GAP; help for <Ref Func="Edit"/>. If you want to
use the editor defined in your (shell) environment then leave the
<C>Editor</C> and <C>EditorOptions</C> preferences empty.

<P/>

The defaults are computed at runtime.
</Item>
<Mark>
<Index Key='ExcludeFromAutoload'><C>ExcludeFromAutoload</C></Index>
<C>ExcludeFromAutoload</C>
</Mark>
<Item>
These packages are not loaded at &GAP; startup. This doesn't work for packages
which are needed by the &GAP; library, or which are already loaded in a
workspace.

<P/>

Default: <C>""</C>.
</Item>
<Mark>
<Index Key='HelpViewers'><C>HelpViewers</C></Index>
<Index Key='XpdfOptions'><C>XpdfOptions</C></Index>
<Index Key='XdviOptions'><C>XdviOptions</C></Index>
<C>HelpViewers</C>,
<C>XpdfOptions</C>,
<C>XdviOptions</C>
</Mark>
<Item>
Here you can choose your preferred help viewers. See the help for <Ref
Func="SetHelpViewer"/> for further options.
<P/>
Try <C>HelpViewers:= [ "screen", "firefox", "xpdf" ];</C>.
<P/>
(For <C>"screen"</C> we also suggest to set the <C>Pager</C> entry to
<C>"less"</C>.)

<P/>

Defaults: <C>[ [ "screen" ], "", "" ]</C>.
</Item>
<Mark>
<Index Key='HistoryBackwardSearchSkipIdenticalEntries'><C>HistoryBackwardSearchSkipIdenticalEntries</C></Index>
<C>HistoryBackwardSearchSkipIdenticalEntries</C>
</Mark>
<Item>
When a command is executed multiple times, it is also stored in history
multiple times. Setting this option to <K>true</K> skips identical entries
when searching backwards in history.

<P/>

Admissible values:
<K>true</K>,
<K>false</K>.

<P/>

Default: <K>false</K>.
</Item>
<Mark>
<Index Key='HistoryMaxLines'><C>HistoryMaxLines</C></Index>
<Index Key='SaveAndRestoreHistory'><C>SaveAndRestoreHistory</C></Index>
<C>HistoryMaxLines</C>,
<C>SaveAndRestoreHistory</C>
</Mark>
<Item>
<C>HistoryMaxLines</C> is the maximal amount of input lines held in &GAP;'s
command line history.
<P/>
If <C>SaveAndRestoreHistory</C> is <K>true</K> then &GAP; saves its command
line history before terminating a &GAP; session, and prepends the stored
history when &GAP; is started. If this is enabled it is suggested to set
<C>HistoryMaxLines</C> to some finite value. It is also possible to set
<C>HistoryMaxLines</C> to <Ref Var="infinity"/> to keep arbitrarily many
lines.
<P/>
These preferences are ignored if &GAP; was not compiled with readline support.

<P/>

Defaults: <C>[ 10000, true ]</C>.
</Item>
<Mark>
<Index Key='InfoPackageLoadingLevel'><C>InfoPackageLoadingLevel</C></Index>
<C>InfoPackageLoadingLevel</C>
</Mark>
<Item>
Info messages concerning package loading up to this level are printed. The
level can be changed in a running session using <Ref Oper="SetInfoLevel"/>.

<P/>

Admissible values:
<C>1</C>,
<C>2</C>,
<C>3</C>,
<C>4</C>.

<P/>

Default: <C>1</C>.
</Item>
<Mark>
<Index Key='MaxBitsIntView'><C>MaxBitsIntView</C></Index>
<C>MaxBitsIntView</C>
</Mark>
<Item>
Maximal bit length of integers to <C>View</C> unabbreviated. Default is about
<M>30</M> lines of a <M>80</M> character wide terminal. Set this to <C>0</C>
to avoid abbreviated ints.

<P/>

Default: <C>8000</C>.
</Item>
<Mark>
<Index Key='PartialPermDisplayLimit'><C>PartialPermDisplayLimit</C></Index>
<Index Key='NotationForPartialPerms'><C>NotationForPartialPerms</C></Index>
<C>PartialPermDisplayLimit</C>,
<C>NotationForPartialPerms</C>
</Mark>
<Item>
options for the display of partial perms

<P/>

Defaults: <C>[ 100, "component" ]</C>.
</Item>
<Mark>
<Index Key='TransformationDisplayLimit'><C>TransformationDisplayLimit</C></Index>
<Index Key='NotationForTransformations'><C>NotationForTransformations</C></Index>
<C>TransformationDisplayLimit</C>,
<C>NotationForTransformations</C>
</Mark>
<Item>
options for the display of transformations

<P/>

Defaults: <C>[ 100, "input" ]</C>.
</Item>
<Mark>
<Index Key='PackagesToIgnore'><C>PackagesToIgnore</C></Index>
<C>PackagesToIgnore</C>
</Mark>
<Item>
These packages are not regarded as available. This doesn't work for packages
which are needed by the &GAP; library, or which are already loaded in a
workspace.

<P/>

Default: <C>""</C>.
</Item>
<Mark>
<Index Key='PackagesToLoad'><C>PackagesToLoad</C></Index>
<C>PackagesToLoad</C>
</Mark>
<Item>
A list of names of packages which should be loaded during startup. For
backwards compatibility, the default lists most of packages that were
autoloaded in &GAP; 4.4 (add or remove packages as you like).

<P/>

Default: <C>[ "autpgrp", "alnuth", "crisp", "ctbllib", "factint", "fga", "irredsol", "laguna", "PackageManager", "polenta", "polycyclic", "resclasses", "sophus", "tomlib" ]</C>.
</Item>
<Mark>
<Index Key='Pager'><C>Pager</C></Index>
<Index Key='PagerOptions'><C>PagerOptions</C></Index>
<C>Pager</C>,
<C>PagerOptions</C>
</Mark>
<Item>
For displaying help pages on screen and other things &GAP; has a rudimentary
builtin pager. We recommend using a more sophisticated external program. For
example, when you have the program <C>less</C> on your computer we recommend:
<P/>
<C>Pager := "less";</C>
<P/>
<C>PagerOptions := ["-f", "-r", "-a", "-i", "-M", "-j2"];</C>
<P/>
If you want to use <C>more</C>, we suggest to use the <C>-f</C> option. If you
want to use the pager defined in your environment then leave the <C>Pager</C>
and <C>PagerOptions</C> preferences empty.

<P/>

The defaults are computed at runtime.
</Item>
<Mark>
<Index Key='ReadObsolete'><C>ReadObsolete</C></Index>
<C>ReadObsolete</C>
</Mark>
<Item>
May be useful to say <K>false</K> here to check if you are using commands
which may vanish in a future version of &GAP;

<P/>

Admissible values:
<K>true</K>,
<K>false</K>.

<P/>

Default: <K>true</K>.
</Item>
<Mark>
<Index Key='ReproducibleBehaviour'><C>ReproducibleBehaviour</C></Index>
<C>ReproducibleBehaviour</C>
</Mark>
<Item>
This preference disables code in &GAP; which changes behaviour based on time
spent, and therefore can produce different results depending on how much time
is taken by other programs running on the same computer. This option may lead
to slower or lower-quality results. Note that many algorithms in &GAP; use the
global random number generator, which is NOT affected by this option. This
only tries to ensure the same version of &GAP;, with the same package versions
loaded, on the same machine, running the same code, in a fresh &GAP; session,
will produce the same results.

<P/>

Admissible values:
<K>true</K>,
<K>false</K>.

<P/>

Default: <K>false</K>.
</Item>
<Mark>
<Index Key='ShortBanners'><C>ShortBanners</C></Index>
<C>ShortBanners</C>
</Mark>
<Item>
If this option is set to <K>true</K>, package banners printed during loading
will only show the name, version and description of a package.

<P/>

Admissible values:
<K>true</K>,
<K>false</K>.

<P/>

Default: <K>false</K>.
</Item>
<Mark>
<Index Key='UseColorPrompt'><C>UseColorPrompt</C></Index>
<C>UseColorPrompt</C>
</Mark>
<Item>
In a color capable terminal (almost any terminal application) you can run
&GAP; such that the prompts, the input and output are distinguished by colors.
Options are <K>true</K>, <K>false</K> or some record as explained in the help
section for <Ref Func="ColorPrompt"/>.

<P/>

Default: <K>true</K>.
</Item>
<Mark>
<Index Key='UseColorsInTerminal'><C>UseColorsInTerminal</C></Index>
<C>UseColorsInTerminal</C>
</Mark>
<Item>
Almost all current terminal emulations support color display, setting this to
<K>true</K> implies a default display of most manuals with color markup. It
may influence the display of other things in the future.

<P/>

Admissible values:
<K>true</K>,
<K>false</K>.

<P/>

Default: <K>true</K>.
</Item>
<Mark>
<Index Key='ViewLength'><C>ViewLength</C></Index>
<C>ViewLength</C>
</Mark>
<Item>
A bound for the number of lines printed when <C>View</C>ing some large
objects.

<P/>

Default: <C>3</C>.
</Item>
<Mark>
<Index Key='WhereDepth'><C>WhereDepth</C></Index>
<C>WhereDepth</C>
</Mark>
<Item>
The number of stack frames shown by <C>Where</C> and <C>WhereWithVars</C> when
called without an explicit depth argument, e.g. in the default <C>OnBreak</C>
handler.

<P/>

Default: <C>5</C>.
</Item>
</List>
