RE: [External] : Q3 - how to delete by words, not cut?

[Drew Adams <drew.adams@oracle.com>]

> > Did you try the `my-backward-delete-word' command I defined for you?
>
> Sorry, I didn't try it before. Because I didn't understand it
> by that time (and I have a habbit not to run any code until I
> understand it good enough).

A good habit!  No reason to be sorry for that.

> But now I dived into it and got it...
> Though the function logic is clear, the key binding won't work.
> I tried different keys. Here is the current state:
> 
> (defun tt-delword-backward (arg)
> "Delete backward arg words. (default 1)"
> (interactive "C-;") ; <==============
>  (let ((opt  (point)))
>    (backward-word arg)
>    (delete-region opt (point))))
>
> (defun tt-delword-forward (arg)
> "Delete forward arg words. (default 1)"
> (interactive "C-'") ; <==============
>  (let ((opt  (point)))
>    (forward-word arg)
>    (delete-region opt (point))))
> 
> I tried to set (interactive "b") and (interactive "f")
> for backward and forward respectively.

No.  You need to read up on `interactive'.
This is what I suggested:

  (defun my-backward-delete-word (arg)
    "Delete backard ARG words.
  ARG is the numeric prefix arg (default 1)."
    (interactive "p")
    (let ((opt  (point)))
      (backward-word arg)
      (delete-region opt (point))))

The "p" arg for `interactive' passes the current
numeric prefix arg that a user supplies as the
argument (ARG).  That defaults to 1, if the user
doesn't explicitly provide any prefix arg.

So with no arg it deletes one word (backward).
With `M-1' it does the same thing.  With `M-2'
it deletes two words, etc.

This is common for Emacs commands that act on
things from the cursor position - you can use
the same command and key binding to act on N
things by using `C-u N' (or `M-n' for small #s).

> When "C-;" is set the minibuffers says it's undefined, when letters are set it just type letters. The call by M-x doesn't do the job either.

Fix your `interactive' argument.  It's not a
key description.  `interactive' has nothing to
do with any key binding.  It specifies how
arguments (in this case argument ARG) are
provided when the function's invoked interactively.

I followed that command definition with this:

  Bind it to some key.

IOW: you define a command and you bind that
command to a key (if you want).  If not bound
to a key you can still invoke it, with `M-x'.

The Elisp manual is your friend...

https://www.gnu.org/software/emacs/manual/html_node/elisp/Defining-Commands.html

https://www.gnu.org/software/emacs/manual/html_node/elisp/Using-Interactive.html