elisp-string-interpolation.el

elisp-string-interpolation.el

(defmacro fmt (str)
  "Elisp string interpolation.

Example:

(fmt \"My name is #{user-full-name}, I am running Emacs #{(if (display-graphic-p) \\\"with a GUI\\\" \\\"in a terminal\\\".)}\""
  (let ((exprs nil))
    (with-temp-buffer
      (insert str)
      (goto-char 1)
      (while (re-search-forward "#{" nil t 1)
        (let ((here (point))
              (emptyp (eql (char-after) ?})))
          (unless  emptyp (push (read (buffer-substring (point) (progn (forward-sexp 1) (point)))) exprs))
          (delete-region (- here 2) (progn (search-forward "}") (point)))
          (unless emptyp (insert "%s"))
          (ignore-errors (forward-char 1))))
      (append (list 'format (buffer-string)) (reverse exprs)))))
      

;; evaluating
(fmt "My name is #{user-full-name}, I am running Emacs #{(if (display-graphic-p) \"with a GUI\" \"in a terminal\".)}")
;; => "My name is Jordon Biondo, I am running Emacs with a GUI"

;; how it expands
(cl-prettyexpand '(fmt "My name is #{user-full-name}, I am running Emacs #{(if (display-graphic-p) \"with a GUI\" \"in a terminal\".)}"))
;; =>
(format "My name is %s, I am running Emacs %s"
        user-full-name
        (if (display-graphic-p) "with a GUI" "in a terminal" \.))