Re: Partial wdired (edit just filename at the point)

[Tomas Hlavaty]

On Mon 22 Mar 2021 at 09:11, Stefan Monnier <monnier@iro.umontreal.ca> wrote:
> Tomas Hlavaty [2021-03-21 23:17:38] wrote:
>> On Wed 17 Mar 2021 at 22:10, Stefan Monnier <monnier@iro.umontreal.ca> wrote:
>>>> +  (add-hook 'before-change-functions 'wdired--preprocess-line nil t)
>>>   Please use #' rather than ' to quote functions (I know the rest of the
>>>   code here doesn't (yet), but we should move towards more systematic
>>>   use of #' so as to better catch obsolete functions and other issues).  ]
>> That is a strange advice.  I would expect #' to remove the indirection
>> via symbol with consequence, that redefining the named function would
>> not be reflected in the original #' value.
>> What is the difference between #' and ' in emacs lisp?
>> Is it different from Common Lisp?
>
> Yes, it's indeed different from Common Lisp: it doesn't have the same
> effect as `symbol-function`.
>
> In ELisp, when quoting a symbol, #' only tells Emacs that the intention
> is to refer to the function by that name more than the symbol itself,
> but semantically, it's almost identical to ' and almost always just
> returns the symbol.  The "almost" is for the exception of references to
> lexically scoped functions (where #' works like in Common Lisp).
>
> Lexically-scoped functions occur most directly via `cl-flet` and
> `cl-labels`, but they can also occur more indirectly via things like
> `cl-defmethod` (where `cl-call-next-method` is lexically scoped) or
> `named-let` (which rely on `cl-flet` or `cl-labels` internally).

Thanks for the great explanation!

Emacs Lisp:

   (type-of 'type-of)
   -> symbol
   (type-of #'type-of)
   -> symbol
   (type-of (lambda () 42))
   -> cons
   (type-of #'(lambda () 42))
   -> cons

Common Lisp:

   (type-of 'type-of)
   -> SYMBOL
   (type-of #'type-of)
   -> FUNCTION
   (type-of (lambda () 42))
   -> FUNCTION
   (type-of #'(lambda () 42))
   -> FUNCTION