-program. It only affects secondary features: indentation and Edebug.
-
-@node Backquote
-@section Backquote
-@cindex backquote (list substitution)
-@cindex ` (list substitution)
-@findex `
-
- Macros often need to construct large list structures from a mixture of
-constants and nonconstant parts. To make this easier, use the @samp{`}
-syntax (usually called @dfn{backquote}).
-
- Backquote allows you to quote a list, but selectively evaluate
-elements of that list. In the simplest case, it is identical to the
-special form @code{quote} (@pxref{Quoting}). For example, these
-two forms yield identical results:
-
-@example
-@group
-`(a list of (+ 2 3) elements)
- @result{} (a list of (+ 2 3) elements)
-@end group
-@group
-'(a list of (+ 2 3) elements)
- @result{} (a list of (+ 2 3) elements)
-@end group
-@end example
-
-@findex , @r{(with backquote)}
-The special marker @samp{,} inside of the argument to backquote
-indicates a value that isn't constant. Backquote evaluates the
-argument of @samp{,} and puts the value in the list structure:
-
-@example
-@group
-(list 'a 'list 'of (+ 2 3) 'elements)
- @result{} (a list of 5 elements)
-@end group
-@group
-`(a list of ,(+ 2 3) elements)
- @result{} (a list of 5 elements)
-@end group
-@end example
-
- Substitution with @samp{,} is allowed at deeper levels of the list
-structure also. For example:
-
-@example
-@group
-(defmacro t-becomes-nil (variable)
- `(if (eq ,variable t)
- (setq ,variable nil)))
-@end group
-
-@group
-(t-becomes-nil foo)
- @equiv{} (if (eq foo t) (setq foo nil))
-@end group
-@end example
-
-@findex ,@@ @r{(with backquote)}
-@cindex splicing (with backquote)
- You can also @dfn{splice} an evaluated value into the resulting list,
-using the special marker @samp{,@@}. The elements of the spliced list
-become elements at the same level as the other elements of the resulting
-list. The equivalent code without using @samp{`} is often unreadable.
-Here are some examples:
-
-@example
-@group
-(setq some-list '(2 3))
- @result{} (2 3)
-@end group
-@group
-(cons 1 (append some-list '(4) some-list))
- @result{} (1 2 3 4 2 3)
-@end group
-@group
-`(1 ,@@some-list 4 ,@@some-list)
- @result{} (1 2 3 4 2 3)
-@end group
-
-@group
-(setq list '(hack foo bar))
- @result{} (hack foo bar)
-@end group
-@group
-(cons 'use
- (cons 'the
- (cons 'words (append (cdr list) '(as elements)))))
- @result{} (use the words foo bar as elements)
-@end group
-@group
-`(use the words ,@@(cdr list) as elements)
- @result{} (use the words foo bar as elements)
-@end group
-@end example