Commit d5c99c9e authored by Richard M. Stallman's avatar Richard M. Stallman
Browse files

(Defining Macros): Give definition of `declare'

(Indenting Macros): New node.
parent 5b2a9a76
......@@ -30,6 +30,7 @@ instead. @xref{Inline Functions}.
* Backquote:: Easier construction of list structure.
* Problems with Macros:: Don't evaluate the macro arguments too many times.
Don't hide the user's variables.
* Indenting Macros:: Specifying how to indent macro calls.
@end menu
@node Simple Macro
......@@ -205,6 +206,30 @@ any @code{interactive} declaration is ignored since macros cannot be
called interactively.
@end defspec
The body of the macro definition can include a @code{declare} form,
which can specify how @key{TAB} should indent macro calls, and how to
step through them for Edebug.
@defspec declare @var{specs}...
This special form is used at top level in a macro definition to
specify various additional information about it. Two kinds of
specification are currently supported:
@table @code
@item (edebug @var{edebug-form-spec})
Specify how to step through macro calls for Edebug.
@xref{Instrumenting Macro Calls}, for more details.
@item (indent @var{indent-spec})
Specify how to indent calls to this macro. @xref{Indenting Macros},
for more details.
@end table
@end defspec
No macro absolutely needs a @code{declare} form, because that form
has no effect on how the macro expands, on what the macro means in the
program. It only affects secondary features: indentation and Edebug.
@node Backquote
@section Backquote
@cindex backquote (list substitution)
......@@ -636,3 +661,58 @@ One way to avoid pathological cases like this is to think of
allocation construct. You wouldn't use @code{setcar} on a constant such
as @code{'(nil)}, so naturally you won't use it on @code{(empty-object)}
either.
@node Indenting Macros
@section Indenting Macros
You can use the @code{declare} form in the macro definition to
specify how to @key{TAB} should indent indent calls to the macro. You
write it like this:
@example
(declare (indent @var{indent-spec}))
@end example
@noindent
Here are the possibilities for @var{indent-spec}:
@table @asis
@item @code{nil}
This is the same as no property---use the standard indentation pattern.
@item @code{defun}
Handle this function like a @samp{def} construct: treat the second
line as the start of a @dfn{body}.
@item a number, @var{number}
The first @var{number} arguments of the function are
@dfn{distinguished} arguments; the rest are considered the body
of the expression. A line in the expression is indented according to
whether the first argument on it is distinguished or not. If the
argument is part of the body, the line is indented @code{lisp-body-indent}
more columns than the open-parenthesis starting the containing
expression. If the argument is distinguished and is either the first
or second argument, it is indented @emph{twice} that many extra columns.
If the argument is distinguished and not the first or second argument,
the line uses the standard pattern.
@item a symbol, @var{symbol}
@var{symbol} should be a function name; that function is called to
calculate the indentation of a line within this expression. The
function receives two arguments:
@table @asis
@item @var{state}
The value returned by @code{parse-partial-sexp} (a Lisp primitive for
indentation and nesting computation) when it parses up to the
beginning of this line.
@item @var{pos}
The position at which the line being indented begins.
@end table
@noindent
It should return either a number, which is the number of columns of
indentation for that line, or a list whose car is such a number. The
difference between returning a number and returning a list is that a
number says that all following lines at the same nesting level should
be indented just like this one; a list says that following lines might
call for different indentations. This makes a difference when the
indentation is being computed by @kbd{C-M-q}; if the value is a
number, @kbd{C-M-q} need not recalculate indentation for the following
lines until the end of the list.
@end table
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