Add utility function/binding to evaluate math in place

.emacs.d/init.el

@@ -334,6 +334,18 @@
   (add-hook 'yaml-mode-hook
             (lambda () (setq-local show-trailing-whitespace t))))
 
+(use-package calc
+  :bind ("C-x M-e" . calc-eval-in-place)
+  :init
+  (defun calc-eval-in-place ()
+    (interactive)
+    (let ((result (calc-eval (buffer-substring-no-properties (point) (mark)))))
+      (if (stringp result)
+          (progn
+            (delete-region (point) (mark))
+            (insert result))
+        (apply 'user-error "Error at charater %d: %s" result)))))
+
 ;;;; external packages (required)
 (use-package auto-package-update :ensure
   :commands auto-package-update-cli