Question

For example if I have the text:

Sum of items is (+ 1 2 3)

I want to move to the end of the line, evaluate the expression and replace it with the result, so that it reads:

Sum of items is 6

Answer 1

With the cursor at the end of the line, C-u C-x C-e will insert the value of the preceding parenthesized expression into the buffer. You could do that, then manually back up and delete the original expression. If that’s too much work, here’s a command that evaluates the preceding expression and replaces it with its value:

  (defun replace-last-sexp ()
    (interactive)
    (let ((value (eval (preceding-sexp))))
      (kill-sexp -1)
      (insert (format "%S" value))))