+ <p><bf/Note:/ There will be no warning if an environment variable
+ is not defined. The result will of the expansion will then be empty.
+
+ <sect1>Configuration Variables
+
+ <p>As for environment variables, the values of all configuration
+ variables as string can be used in the same way, too. For example,
+
+<tscreen><verb>
+set imap_home_namespace = $folder
+</verb></tscreen>
+
+ <p>would set the value of <ref id="imap_home_namespace"
+ name="$imap_home_namespace"> to the value to
+ which <ref id="folder" name="$folder"> is <em/currently/ set
+ to.
+
+ <p><bf/Note:/ There're no logical links established in such cases so
+ that the the value for <ref id="imap_home_namespace"
+ name="$imap_home_namespace"> won't change even
+ if <ref id="folder" name="$folder"> gets changed.
+
+ <p><bf/Note:/ There will be no warning if a configuration variable
+ is not defined or is empty. The result will of the expansion will
+ then be empty.
+
+ <sect1>Self-Defined Variables
+
+ <p>Mutt-ng flexibly allows users to define their own variables. To
+ avoid conflicts with the standard set and to prevent misleading
+ error messages, there's a reserved namespace for them: all
+ user-defined variables must be prefixed with <tt/user_/ and can be
+ used just like any ordinary configuration or environment
+ variable.
+
+ <p>For example, to view the manual, users can either define three
+ macros like the following
+
+<tscreen><verb>
+macro generic <F1> "!less -r /path/to/manual" "Show manual"
+macro pager <F1> "!less -r /path/to/manual" "Show manual"
+macro index <F1> "!less -r /path/to/manual" "Show manual"
+</verb></tscreen>
+
+ <p>for <tt/generic/, <tt/pager/ and <tt/index/. The alternative is to
+ define a custom variable like so:
+
+<tscreen><verb>
+set user_manualcmd = '!less -r /path/to_manual"
+macro generic <F1> "$user_manualcmd<enter>" "Show manual"
+macro pager <F1> "$user_manualcmd<enter>" "Show manual"
+macro index <F1> "$user_manualcmd<enter>" "Show manual"
+</verb></tscreen>
+
+ <p>Using this feature, arbitrary sequences can be defined once and
+ recalled and reused where necessary. More advanced scenarios could
+ include to save a variable's value at the beginning of macro
+ sequence and restore it at end.
+
+ <p>When the variable is first defined, the first value it gets
+ assigned is also the initial value to which it can be reset using
+ the <tt/reset/ command.
+
+ <p>The complete removal is done via the <tt/unset/ keyword.
+
+ <p>After the following sequence:
+
+<tscreen><verb>
+set user_foo = 42
+set user_foo = 666
+</verb></tscreen>
+
+ <p>the variable <tt>$user_foo</tt> has a current value of 666 and an
+ initial of 42. The query
+
+<tscreen><verb>
+set ?user_foo
+</verb></tscreen>
+
+ <p>will show 666. After doing the reset via
+
+<tscreen><verb>
+reset user_foo
+</verb></tscreen>
+
+ <p>a following query will give 42 as the result. After unsetting it
+ via
+
+<tscreen><verb>
+unset user_foo
+</verb></tscreen>
+
+ <p>any query or operation (except the noted expansion within other
+ statements) will lead to an error message.
+
+ <sect1>Type Conversions
+
+ <p>A note about variable's types during conversion: internally
+ values are stored in internal types but for any dump/query or set
+ operation they're converted to and from string. That means that
+ there's no need to worry about types when referencing any variable.
+ As an example, the following can be used without harm (besides
+ makeing muttng very likely behave strange):
+
+<tscreen><verb>
+set read_inc = 100
+set folder = $read_inc
+set read_inc = $folder
+set user_magic_number = 42
+set folder = $user_magic_number
+</verb></tscreen>
+
+<!--}}}-->