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The description of C-x C-e mentions:

...Interactively, with a non '-' prefix argument, print output into current buffer.

I understand this to mean this logic is triggered when I issue C-u C-x C-e, but how would I bind this to C-c c? How do I specify the prefix in the binding?

Same for C-SPC:

With prefix argument (e.g., C-u C-SPC), jump to the mark, and set the mark from position popped off the local mark ring (this does not affect the global mark ring).

My normal binding looks like this:

(global-set-key (kbd "C-c ,") 'pop-global-mark)
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2 Answers 2

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C-u invokes the function universal-argument, and you want to ensure that eval-last-sexp is called as if you invoked it interactively, which is done with call-interactively. You can simulate universal-argument by let-binding current-prefix-arg.

Putting that all together for C-u C-x C-e:

(global-set-key (kbd "C-c c") (lambda () (interactive) (let ((current-prefix-arg 1)) (call-interactively #'eval-last-sexp))))

For C-u C-SPC:

(global-set-key (kbd "C-c ,") (lambda () (interactive) (let ((current-prefix-arg '(4))) (call-interactively #'set-mark-command))))

Strictly speaking, as @NickD points out, current-prefix-arg should be bound to '(4) to be exactly equivalent to C-u, but for eval-last-sexp that doesn't matter.

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  • 1
    If you want to emulate C-u, then current-prefix-arg should be set to (4) - no? 1 emulates C-u 1. Commented Sep 24, 2020 at 12:42
  • It depends on the function you're calling. If it just checks whether or not there is a prefix arg, it doesn't matter. I'll clarify the answer Commented Sep 24, 2020 at 12:46
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@rpluim gives us the answer and inspires me to produce this handy-dandy Lisp macro. (I'm only presenting it as an "answer" to get the formatting)

(cl-defmacro ph/defprefixed (command &key (prefix 4) no-read-only) `(defun ,(intern (format "ph/prefixed-%s" command)) () ,(format "Execute `%s' with prefix argument." command) (interactive ,(when no-read-only "*")) (let ((current-prefix-arg (list ,prefix))) (call-interactively (function ,command)))))

Used thus:

(ph/defprefixed set-mark-command)

it expands to this:

(defun ph/prefixed-set-mark-command () "Execute `set-mark-command' with prefix argument." (interactive nil) ; nil is ignored (let ((current-prefix-arg (list 4))) (call-interactively (function set-mark-command))))

And thus:

(ph/defprefixed eval-last-sexp :no-read-only t)

Expansion:

(defun ph/prefixed-eval-last-sexp () "Execute `eval-last-sexp' with prefix argument." (interactive "*") (let ((current-prefix-arg (list 4))) (call-interactively (function eval-last-sexp))))
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