executing a lisp command as a hook

executing a lisp command as a hook

[mmuurr]

Hi all, I'm fairly new with emacs, so please bear with me if this is a
trivial question...

I have a hook variable that I'm trying to set.  It's a variable
included in the JDE (Java Development Environment) for Emacs, and the
goal is for me to be able to display some text in the echo area when I
switch from project to project between buffers.

There is a variable associated with each project called
jde-project-name.

When I jump to a new project, I simply want to be notified of this in
the echo area.

So I tried a simple elisp function:

(message jde-project-name)

This works when I execute the command from a scratch buffer using C-c
C-e, but if I include that command as is in the hook line (set using a
configure-variable interface) I get this is a response in the echo
area:

Invalid function: (message jde-project-name)

Can anyone tell me how to provide a way to call an elisp function from
a hook variable?

Thanks!

Re: executing a lisp command as a hook

[mmuurr]

OK, I figured it out!  I'm doing the correct thing, however a whole
bunch of messages are displayed before and after the hook executes, so
I lose it in the echo area.  Is there anyway to put a time on a
message, so it lingers in the echo area (maybe as other commands flash
by, but then goes back to the important status message I want).

Better yet, can anyone tell me how to append some information to the
information bar at the bottom of each window (the one that shows things
like line number, major-minor modes, etc...)

Thanks!

RE: executing a lisp command as a hook

[Drew Adams]

    Is there anyway to put a time on a
    message, so it lingers in the echo area (maybe as other commands flash
    by, but then goes back to the important status message I want).

See function `sit-for' (and perhaps function `sleep-for').
    
    Better yet, can anyone tell me how to append some information to the
    information bar at the bottom of each window (the one that shows things
    like line number, major-minor modes, etc...)
    
Look up `mode-line' in the Emac-Lisp manual.

Re: executing a lisp command as a hook

[Steinar Bang]

>>>>> mmuurr@gmail.com:

> So I tried a simple elisp function:

> (message jde-project-name)

> This works when I execute the command from a scratch buffer using C-c
> C-e, but if I include that command as is in the hook line (set using a
> configure-variable interface) I get this is a response in the echo
> area:

> Invalid function: (message jde-project-name)

I'm guessing that's because (message jde-project-name) by itself isn't
a function.  It's a function call.

Did you try doing something like this?
 (add-hook 'my-hook '(message jde-project-name))
?

> Can anyone tell me how to provide a way to call an elisp function from
> a hook variable?

You can use an anonymous lambda function, or define a function with a
name and use the name.  I prefer using named functions, because they
are easier to recognize when looking at the hook's value, and easier
to remove.

Using a lambda it would be something like this:
 (add-hook 'my-hook '(lambda () (message jde-project-name)))

Using a named function it would be something like this 
 (defun display-jde-project-name () (message jde-project-name))
 (add-hook 'my-hook 'display-jde-project-name)

(though as was hinted at later in this thread, message may not be the
best function to use here)