@comment node-name, next, previous, up
@section Basic Types
-The syntax of a type specification is given below:
+This is the general syntax of a type specification:
@example
-NAME ::= (NAME [KEYWORD ARGUMENT]... ARGS)
- | NAME
+@var{name} ::= (@var{name} [@var{keyword} @var{argument}]... @var{args})
+ | @var{name}
@end example
Where, @var{name} is a widget name, @var{keyword} is the name of a
Syntax:
@example
-TYPE ::= (link [KEYWORD ARGUMENT]... [ VALUE ])
+@var{type} ::= (link [@var{keyword} @var{argument}]... [ @var{value} ])
@end example
The @var{value}, if present, is used to initialize the @code{:value}
Syntax:
@example
-TYPE ::= (url-link [KEYWORD ARGUMENT]... URL)
+@var{type} ::= (url-link [@var{keyword} @var{argument}]... @var{url})
@end example
@findex browse-url-browser-function@r{, and @code{url-link} widget}
Syntax:
@example
-TYPE ::= (info-link [KEYWORD ARGUMENT]... ADDRESS)
+@var{type} ::= (info-link [@var{keyword} @var{argument}]... @var{address})
@end example
When this link is invoked, the built-in Info reader is started on
Syntax:
@example
-TYPE ::= (push-button [KEYWORD ARGUMENT]... [ VALUE ])
+@var{type} ::= (push-button [@var{keyword} @var{argument}]... [ @var{value} ])
@end example
The @var{value}, if present, is used to initialize the @code{:value}
Syntax:
@example
-TYPE ::= (editable-field [KEYWORD ARGUMENT]... [ VALUE ])
+@var{type} ::= (editable-field [@var{keyword} @var{argument}]... [ @var{value} ])
@end example
The @var{value}, if present, is used to initialize the @code{:value}
Syntax:
@example
-TYPE ::= (menu-choice [KEYWORD ARGUMENT]... TYPE ... )
+@var{type} ::= (menu-choice [@var{keyword} @var{argument}]... @var{type} ... )
@end example
The @var{type} argument represents each possible choice. The widget's
Syntax:
@example
-TYPE ::= (radio-button-choice [KEYWORD ARGUMENT]... TYPE ... )
+@var{type} ::= (radio-button-choice [@var{keyword} @var{argument}]... @var{type} ... )
@end example
-The @var{type} argument represents each possible choice. The widget's
-value will be that of the chosen @var{type} argument. This widget will
-match any value matching at least one of the specified @var{type}
-arguments.
+The component types specify the choices, with one radio button for
+each. The widget's value will be that of the chosen @var{type}
+argument. This widget matches any value that matches at least one of
+the specified @var{type} arguments.
The following extra properties are recognized.
Syntax:
@example
-ITEM ::= (item [KEYWORD ARGUMENT]... VALUE)
+@var{item} ::= (item [@var{keyword} @var{argument}]... @var{value})
@end example
The @var{value}, if present, is used to initialize the @code{:value}
Syntax:
@example
-ITEM ::= (choice-item [KEYWORD ARGUMENT]... VALUE)
+@var{item} ::= (choice-item [@var{keyword} @var{argument}]... @var{value})
@end example
The @var{value}, if present, is used to initialize the @code{:value}
Syntax:
@example
-TYPE ::= (toggle [KEYWORD ARGUMENT]...)
+@var{type} ::= (toggle [@var{keyword} @var{argument}]...)
@end example
The widget has two possible states, @samp{on} and @samp{off}, which
Syntax:
@example
-TYPE ::= (checkbox [KEYWORD ARGUMENT]...)
+@var{type} ::= (checkbox [@var{keyword} @var{argument}]...)
@end example
@node checklist, editable-list, checkbox, Basic Types
Syntax:
@example
-TYPE ::= (checklist [KEYWORD ARGUMENT]... TYPE ... )
+@var{type} ::= (checklist [@var{keyword} @var{argument}]... @var{type} ... )
@end example
The @var{type} arguments represent each checklist item. The widget's
Syntax:
@example
-TYPE ::= (editable-list [KEYWORD ARGUMENT]... TYPE)
+@var{type} ::= (editable-list [@var{keyword} @var{argument}]... @var{type})
@end example
The value is a list, where each member represents one widget of type
Syntax:
@example
-TYPE ::= (group [KEYWORD ARGUMENT]... TYPE...)
+@var{type} ::= (group [@var{keyword} @var{argument}]... @var{type}...)
@end example
The value is a list, with one member for each @var{type}.
The syntax for the @code{const} widget is:
@example
-TYPE ::= (const [KEYWORD ARGUMENT]... [ VALUE ])
+@var{type} ::= (const [@var{keyword} @var{argument}]... [ @var{value} ])
@end example
The @var{value}, if present, is used to initialize the @code{:value}
The syntax for the @code{sexp} widget is:
@example
-TYPE ::= (sexp [KEYWORD ARGUMENT]... [ VALUE ])
+@var{type} ::= (sexp [@var{keyword} @var{argument}]... [ @var{value} ])
@end example
@deffn Widget sexp
The syntax for all the atoms are:
@example
-TYPE ::= (NAME [KEYWORD ARGUMENT]... [ VALUE ])
+@var{type} ::= (@var{construct} [@var{keyword} @var{argument}]... [ @var{value} ])
@end example
The @var{value}, if present, is used to initialize the @code{:value}
@subsection Composite Sexp Widgets
@cindex composite sexp widgets
-The syntax for the composite widget is:
+The syntax for the composite widget construct is:
@example
-TYPE ::= (NAME [KEYWORD ARGUMENT]... COMPONENT...)
+@var{type} ::= (@var{construct} [@var{keyword} @var{argument}]... @var{component}...)
@end example
@noindent
will be displayed in the buffer, and will be editable by the user.
@deffn Widget cons
-The value of a @code{cons} widget is a cons-cell where the @sc{car} is
-the value of the first component and the @sc{cdr} is the value of the
-second component. There must be exactly two components.
+The value of a @code{cons} widget must be a cons-cell whose @sc{car}
+and @sc{cdr} have two specified types. It uses this syntax:
+
+@example
+@var{type} ::= (cons [@var{keyword} @var{argument}]... @var{car-type} @var{cdr-type})
+@end example
+@end deffn
+
+@deffn Widget choice
+The value matched by a @code{choice} widget must have one of a fixed
+set of types. The widget's syntax is as follows:
+
+@example
+@var{type} ::= (choice [@var{keyword} @var{argument}]... @var{type} ... )
+@end example
+
+The value of a @code{choice} widget can be anything that matches any of the
+@var{types}.
@end deffn
@deffn Widget list
-The value of a @code{list} widget is a list containing the value of
-each of its components.
+The value of a @code{list} widget must be a list whose element types
+match the specified component types:
+
+@example
+@var{type} ::= (list [@var{keyword} @var{argument}]... @var{component-type}...)
+@end example
+
+Thus, @code{(list string number)} matches lists of two elements,
+the first being a string and the second being a number.
@end deffn
@deffn Widget vector
-The value of a @code{vector} widget is a vector containing the value of
-each of its component.
+The @code{vector} widget is like the @code{list} widget but matches
+vectors instead of lists. Thus, @code{(vector string number)} matches
+vectors of two elements, the first being a string and the second being
+a number.
@end deffn
The above suffice for specifying fixed size lists and vectors. To get
variable length lists and vectors, you can use a @code{choice},
@code{set}, or @code{repeat} widget together with the @code{:inline}
-keyword. If any component of a composite widget has the @code{:inline}
-keyword set, its value must be a list which will then be spliced into
-the composite. For example, to specify a list whose first element must
-be a file name, and whose remaining arguments should either be the
-symbol @code{t} or two files, you can use the following widget
-specification:
+keyword. If any component of a composite widget has the
+@code{:inline} keyword set, its value must be a list which will then
+be spliced into the composite. For example, to specify a list whose
+first element must be a file name, and whose remaining elements should
+either be the symbol @code{t} or two strings (file names), you can use
+the following widget specification:
@example
(list file
@end example
The value of a widget of this type will either have the form
-@code{(file t)} or @code{(file string string)}.
+@code{(file t)} or @code{(file @var{string} @var{string})}.
-This concept of inline is probably hard to understand. It was certainly
-hard to implement, so instead of confusing you more by trying to explain
-it here, I'll just suggest you meditate over it for a while.
-
-@deffn Widget choice
-Allows you to edit a sexp which may have one of a fixed set of types.
-It is currently implemented with the @code{choice-menu} basic widget,
-and has a similar syntax.
-@end deffn
+This concept of @code{:inline} may be hard to understand. It was
+certainly hard to implement, so instead of confusing you more by
+trying to explain it here, I'll just suggest you meditate over it for
+a while.
@deffn Widget set
-Allows you to specify a type which must be a list whose elements all
-belong to the given set. The elements of the list are not significant.
-This is implemented on top of the @code{checklist} basic widget, and has
-a similar syntax.
+Specifies a type whose values are the lists whose elements all belong
+to a given set. The order of elements of the list is not significant.
+Here's the syntax:
+
+@example
+@var{type} ::= (set [@var{keyword} @var{argument}]... @var{permitted-element} ... )
+@end example
+
+Use @code{const} to specify each permitted element, like this:
+@code{(set (const a) (const b))}.
@end deffn
@deffn Widget repeat
-Allows you to specify a variable length list whose members are all of
-the same type. Implemented on top of the @code{editable-list} basic
-widget, and has a similar syntax.
+Specifies a list of any number of elements that fit a certain type.
+
+@example
+@var{type} ::= (repeat [@var{keyword} @var{argument}]... @var{type})
+@end example
@end deffn
@node Widget Properties, Defining New Widgets, Sexp Types, Top