Re: Trouble using a lambda in the key-translation-map

[Barry OReilly]

>>   (defun my-translate-key (prompt) (interactive) (kbd "C-c"))
>>   (define-key key-translation-map (kbd "C-e") (lambda (prompt)
>> (interactive) (kbd "C-c"))) ; Doesn't work
>>   (define-key key-translation-map (kbd "C-e") 'my-translate-key) ; Works

> Look at the description of define-key -- the third argument has to be a
> SYMBOL for it to be treated as a function.  Lambda doesn't return a
> function, it returns a list.

Yet this works:
   (define-key global-map (kbd "C-e") (lambda () (interactive)
(message "Inside C-e's lambda")))
C-e displays the message without going to the end of the line, as expected.

I thought wherever functions are passed, a lambda could be passed
instead.  The Elisp manual corroborates this in section 12.7 Anonymous
Functions: "Anonymous functions are valid wherever function names
are.".  I don't see where my misunderstanding is.

I tried another thing in scratch:
  (progn
    (fset 'foo (lambda (prompt) (message "Inside lambda.") (kbd "C-c")))
    (define-key key-translation-map (kbd "C-e") 'foo)
    )

This behaves as I'd expect; I see "Inside lambda" and a translation to
C-c.  Thus it would seem the type returned from the lambda form is not
the problem.

The reason I ask is because I'm trying to create a generalized way to
make key translations that either translate to another key or to
itself based on an evaluated predicate.  My approach was:

(defun make-conditional-key-translation (key-from key-to translate-keys-p)
  "Make a Key Translation such that if the translate-keys-p function
returns true,
key-from translates to key-to, else key-from translates to itself.
translate-keys-p
takes no args. "
  (define-key key-translation-map key-from
              (lambda (prompt)
                      (if (funcall translate-keys-p) key-to key-from)))
  )
(defun my-translate-keys-p ()
  "Returns whether conditional key translations should be active.  See
make-conditional-key-translation function. "
  (or (evil-motion-state-p) (evil-normal-state-p) (evil-visual-state-p))
  )
(make-conditional-key-translation (kbd "ce") (kbd "C-e") 'my-translate-keys-p)