`read-file-name' with history?

`read-file-name' with history?

[Elena]

Hello,

unlike `read-string', `read-file-name' lacks an history parameter.  Is
there a way to achieve such behavior?

Since `read-string' is a built-in function in C source code, I can't
examine it (well, I could examine the C sources, but I think it would
be a little difficult).

Any help?  Thanks.

RE: `read-file-name' with history?

[Drew Adams]

> unlike `read-string', `read-file-name' lacks an history parameter.  Is
> there a way to achieve such behavior?

Correct, there is no history parameter.  But it does use a history list:
`file-name-history'.

To achieve a file-name reading behavior with an arbitrary history list, you
would need to write your own file-name reading function and bind it to the
variable `read-file-name-function'.  Then let-bind that var around a call to
`read-file-name.

> Since `read-string' is a built-in function in C source code, I can't
> examine it (well, I could examine the C sources, but I think it would
> be a little difficult).

What is the question here?  What is the relation to your question about
`read-file-name''s history parameter?

Re: `read-file-name' with history?

[egarrulo]

Hello Drew,

2010/12/10 Drew Adams <drew.adams@oracle.com>:
>> unlike `read-string', `read-file-name' lacks an history parameter.  Is
>> there a way to achieve such behavior?
>
> Correct, there is no history parameter.  But it does use a history list:
> `file-name-history'.
>
> To achieve a file-name reading behavior with an arbitrary history list, you
> would need to write your own file-name reading function and bind it to the
> variable `read-file-name-function'.  Then let-bind that var around a call to
> `read-file-name.
>
>> Since `read-string' is a built-in function in C source code, I can't
>> examine it (well, I could examine the C sources, but I think it would
>> be a little difficult).
>
> What is the question here?  What is the relation to your question about
> `read-file-name''s history parameter?

My problem is that writing such a function is beyond my current
capabilities.  I usually manage to achieve such goals by modifying
some existing Lisp code.  In this case, however, no Lisp code is
available.  That's why I was asking for pointers.

RE: `read-file-name' with history?

[Drew Adams]

> >> unlike `read-string', `read-file-name' lacks an history 
> >> parameter.  Is there a way to achieve such behavior?
> >
> > Correct, there is no history parameter.  But it does use a 
> > history list: `file-name-history'.
> >
> > To achieve a file-name reading behavior with an arbitrary 
> > history list, you would need to write your own file-name
> > reading function and bind it to the variable
> > `read-file-name-function'.  Then let-bind that var around
> > a call to `read-file-name.
> >
> >> Since `read-string' is a built-in function in C source 
> >> code, I can't examine it (well, I could examine the C
> >> sources, but I think it would be a little difficult).
> >
> > What is the question here?  What is the relation to your 
> > question about `read-file-name''s history parameter?
> 
> My problem is that writing such a function is beyond my current
> capabilities.  I usually manage to achieve such goals by modifying
> some existing Lisp code.  In this case, however, no Lisp code is
> available.  That's why I was asking for pointers.

OK, but the Lisp code for `read-file-name' is available.
From there you can see that `file-name-history' is used.

Instead of defining your own function for `read-file-name-function', you can
also just define a function that explicitly adds whatever file name is read to a
history that you pass it.  In order to not also add that name to the regular
`file-name-history' you need to bind that var so it gets restored when your
function exits.  For example:

(defvar my-history () "Once upon a time...")

(defun my-read-file-name (prompt &optional dir default-filename
                          mustmatch initial predicate history)
  (let* ((file-name-history  file-name-history)
	   (file  (read-file-name prompt dir default-filename
			              mustmatch initial predicate)))
    (add-to-list history file)
    file))

Now try:
(my-read-file-name "File: " nil nil t nil nil 'my-history)

C-h v my-history
C-h v file-name-history

And compare with: (read-file-name "File: " nil nil t)

Re: `read-file-name' with history?

[egarrulo]

Thank you Drew.  Another guy kindly sent me another implementation of
`read-file-name' with history.  I'll study both examples.

Indeed you are right: `read-file-name' is defined into "minibuffer.el"
in Emacs 23.2.  I'm using Emacs 22.3, where it is defined in C source,
therefore I didn't notice.

Have a nice day ;-)
Elena


2010/12/10 Drew Adams <drew.adams@oracle.com>:
>> >> unlike `read-string', `read-file-name' lacks an history
>> >> parameter.  Is there a way to achieve such behavior?
>> >
>> > Correct, there is no history parameter.  But it does use a
>> > history list: `file-name-history'.
>> >
>> > To achieve a file-name reading behavior with an arbitrary
>> > history list, you would need to write your own file-name
>> > reading function and bind it to the variable
>> > `read-file-name-function'.  Then let-bind that var around
>> > a call to `read-file-name.
>> >
>> >> Since `read-string' is a built-in function in C source
>> >> code, I can't examine it (well, I could examine the C
>> >> sources, but I think it would be a little difficult).
>> >
>> > What is the question here?  What is the relation to your
>> > question about `read-file-name''s history parameter?
>>
>> My problem is that writing such a function is beyond my current
>> capabilities.  I usually manage to achieve such goals by modifying
>> some existing Lisp code.  In this case, however, no Lisp code is
>> available.  That's why I was asking for pointers.
>
> OK, but the Lisp code for `read-file-name' is available.
> From there you can see that `file-name-history' is used.
>
> Instead of defining your own function for `read-file-name-function', you can
> also just define a function that explicitly adds whatever file name is read to a
> history that you pass it.  In order to not also add that name to the regular
> `file-name-history' you need to bind that var so it gets restored when your
> function exits.  For example:
>
> (defvar my-history () "Once upon a time...")
>
> (defun my-read-file-name (prompt &optional dir default-filename
>                          mustmatch initial predicate history)
>  (let* ((file-name-history  file-name-history)
>           (file  (read-file-name prompt dir default-filename
>                                      mustmatch initial predicate)))
>    (add-to-list history file)
>    file))
>
> Now try:
> (my-read-file-name "File: " nil nil t nil nil 'my-history)
>
> C-h v my-history
> C-h v file-name-history
>
> And compare with: (read-file-name "File: " nil nil t)
>
>
>
>
>