wrong-type-argument from insert yank

Question

I'm looking for ways to get the last copy from the kill ring in Emacs.

I run

(insert (yank))[cursor]

with C-x C-e and I get this *Backtrace*:

Debugger entered--Lisp error: (wrong-type-argument char-or-string-p nil)
  insert(nil)
  eval((insert (yank)) nil)
  elisp--eval-last-sexp(nil)
  eval-last-sexp(nil)
  funcall-interactively(eval-last-sexp nil)
  call-interactively(eval-last-sexp nil nil)
  command-execute(eval-last-sexp)

What I'm trying to do is get the last copied text from the kill-ring (I think it would make it feel more polished if when I call this it removes the last copy from the kill-ring when ran, but I haven't found how to do that yet.), so I can have the defun that calls this get the last think I copied.

The command works correctly, but also calls up this Backtrace. I don't know what the backtrace message wants me to do? I would suspect that I'm not supposed to call yank in this manner.

Answer 1

Let's look at the documentation for yank. From C-h f yank RET:

Reinsert ("paste") the last stretch of killed text.

Oh, so yank doesn't just return the last killed text; it inserts it too. So you can simply run (yank) to put that text into your buffer.

Errors?

So why are we seeing the wrong-type-argument error? Let's run (yank) in IELM, so we can see its return value

ELISP> (yank)
nil
ELISP> I killed this text previously.

Oh! So (yank) returns nil. Amusingly, the inserted text is inserted into IELM's next prompt! To complete the circle, let's try running (insert nil). When I do that, I also get a wrong-type-argument error.