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cl.texi flet clarification

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* doc/misc/cl.texi (Function Bindings): Clarify that cl-flet is lexical.
(Obsolete Macros): Move example here from Function Bindings.

* etc/NEWS: Related edit.
This commit is contained in:
Glenn Morris 2012-11-15 23:43:24 -08:00
parent dedd188497
commit e8693c969a
3 changed files with 34 additions and 21 deletions
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5
doc/misc/ChangeLog
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@ -1,3 +1,8 @@
2012-11-16 Glenn Morris <rgm@gnu.org>
* cl.texi (Function Bindings): Clarify that cl-flet is lexical.
(Obsolete Macros): Move example here from Function Bindings.
2012-11-13 Glenn Morris <rgm@gnu.org>
* erc.texi: Use @code{nil} rather than just "nil".

48
doc/misc/cl.texi
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@ -1292,28 +1292,14 @@ it were a @code{cl-defun} form. The function @var{name} is defined
accordingly for the duration of the body of the @code{cl-flet}; then
the old function definition, or lack thereof, is restored.
You can use @code{cl-flet} to disable or modify the behavior of a
function in a temporary fashion. (Compare this with the idea
of advising functions.
You can use @code{cl-flet} to disable or modify the behavior of
functions (including Emacs primitives) in a temporary, localized fashion.
(Compare this with the idea of advising functions.
@xref{Advising Functions,,,elisp,GNU Emacs Lisp Reference Manual}.)
This will even work on Emacs primitives, although note that some calls
to primitive functions internal to Emacs are made without going
through the symbol's function cell, and so will not be affected by
@code{cl-flet}. For example,
@example
(cl-flet ((message (&rest args) (push args saved-msgs)))
(do-something))
@end example
This code attempts to replace the built-in function @code{message}
with a function that simply saves the messages in a list rather
than displaying them. The original definition of @code{message}
will be restored after @code{do-something} exits. This code will
work fine on messages generated by other Lisp code, but messages
generated directly inside Emacs will not be caught since they make
direct C-language calls to the message routines rather than going
through the Lisp @code{message} function.
The bindings are lexical in scope. This means that all references to
the named functions must appear physically within the body of the
@code{cl-flet} form.
Functions defined by @code{cl-flet} may use the full Common Lisp
argument notation supported by @code{cl-defun}; also, the function
@ -1321,7 +1307,8 @@ body is enclosed in an implicit block as if by @code{cl-defun}.
@xref{Program Structure}.
Note that the @file{cl.el} version of this macro behaves slightly
differently. @xref{Obsolete Macros}.
differently. In particular, its binding is dynamic rather than
lexical. @xref{Obsolete Macros}.
@end defmac
@defmac cl-labels (bindings@dots{}) forms@dots{}
@ -4863,6 +4850,25 @@ time before Emacs had lexical binding). The result is
that @code{flet} affects indirect calls to a function as well as calls
directly inside the @code{flet} form itself.
This will even work on Emacs primitives, although note that some calls
to primitive functions internal to Emacs are made without going
through the symbol's function cell, and so will not be affected by
@code{flet}. For example,
@example
(flet ((message (&rest args) (push args saved-msgs)))
(do-something))
@end example
This code attempts to replace the built-in function @code{message}
with a function that simply saves the messages in a list rather
than displaying them. The original definition of @code{message}
will be restored after @code{do-something} exits. This code will
work fine on messages generated by other Lisp code, but messages
generated directly inside Emacs will not be caught since they make
direct C-language calls to the message routines rather than going
through the Lisp @code{message} function.
@c Bug#411.
Note that many primitives (e.g.@: @code{+}) have special byte-compile
handling. Attempts to redefine such functions using @code{flet} will

2
etc/NEWS
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@ -320,6 +320,8 @@ provide the old non-prefixed names. Some exceptions are listed below.
+++
*** `cl-flet' is not like `flet' (which is deprecated).
Instead it obeys the behavior of Common-Lisp's `flet'.
In particular, in cl-flet function definitions are lexically scoped,
whereas in flet the scoping is dynamic.
+++
*** `cl-labels' is slightly different from `labels'.