[Emacs-diffs] Changes to emacs/lispref/variables.texi

[Richard M. Stallman]

Index: emacs/lispref/variables.texi
diff -c emacs/lispref/variables.texi:1.38 emacs/lispref/variables.texi:1.39
*** emacs/lispref/variables.texi:1.38   Tue Feb  4 09:47:54 2003
--- emacs/lispref/variables.texi        Wed Jun  4 05:25:00 2003
***************
*** 1184,1199 ****
  be changed with @code{setq} in any buffer; the only way to change it is
  with @code{setq-default}.
  
!   @strong{Warning:} When a variable has buffer-local values in one or
! more buffers, binding the variable with @code{let} and changing to a
! different current buffer in which a different binding is in
! effect, and then exiting the @code{let}, the variable may not be
! restored to the value it had before the @code{let}.
! 
!   To preserve your sanity, avoid using a variable in that way.  If you
! use @code{save-excursion} around each piece of code that changes to a
! different current buffer, you will not have this problem
! (@pxref{Excursions}).  Here is an example of what to avoid:
  
  @example
  @group
--- 1184,1200 ----
  be changed with @code{setq} in any buffer; the only way to change it is
  with @code{setq-default}.
  
!   @strong{Warning:} When a variable has buffer-local or frame-local
! bindings in one or more buffers, @code{let} rebinds the binding that's
! currently in effect.  For instance, if the current buffer has a
! buffer-local value, @code{let} temporarily rebinds that.  If no
! buffer-local or frame-local bindings are in effect, @code{let} rebinds
! the default value.  If inside the @code{let} you then change to a
! different current buffer in which a different binding is in effect,
! you won't see the @code{let} binding any more.  And if you exit the
! @code{let} while still in the other buffer, you won't see the
! unbinding occur (though it will occur properly).  Here is an example
! to illustrate:
  
  @example
  @group
***************
*** 1208,1231 ****
    ;; foo @result{} 'g     ; @r{the global value since foo is not local in 
@samp{b}}
    @address@hidden)
  @group
! foo @result{} 'a        ; @r{we are still in buffer @samp{b}, but exiting the 
let}
!                  ; @r{restored the local value in buffer @samp{a}}
  @end group
  @group
! (set-buffer "a") ; @r{This can be seen here:}
! foo @result{} 'a        ; @r{we are back to the local value in buffer 
@samp{a}}
! @end group
! @end example
! 
! @noindent
! But @code{save-excursion} as shown here avoids the problem:
! 
! @example
! @group
! (let ((foo 'temp))
!   (save-excursion
!     (set-buffer "b")
!     @address@hidden))
  @end group
  @end example
  
--- 1209,1220 ----
    ;; foo @result{} 'g     ; @r{the global value since foo is not local in 
@samp{b}}
    @address@hidden)
  @group
! foo @result{} 'g        ; @r{exiting restored the local value in buffer 
@samp{a},}
!                  ; @r{but we don't see that in buffer @samp{b}}
  @end group
  @group
! (set-buffer "a") ; @r{verify the local value was restored}
! foo @result{} 'a
  @end group
  @end example