How do I tell when the current buffer is the minibuffer?

[Alan Mackenzie]

Hello, Emacs.

My problem is as stated in the Subject: line.

Part of my program is being called from `signal_after_change' after
activity in the minibuffer.  However, in that program the buffer local
variables for the main buffer (not the minibuffer) are still in scope.

I need some way of distinguishing that we're in the minibuffer so as to
avoid corrupting the buffer local variables of the selected buffer.

I've tried "Fminibufferp (Qnil);", but this seems just to return nil,
even when the current buffer IS the minibuffer.

I've even tried reading the fine manual without finding anything useful.

Would somebody please tell me what I'm missing.

Thanks!

-- 
Alan Mackenzie (Nuremberg, Germany).