gistfile1.el

(defun logicless-template:emit (string)
  (let ((tokens
         (loop for x in (split-string string "{{")
               nconc
               (cond ((string-match "}}" x)
                      (let ((left (substring x 0 (match-beginning 0)))
                            (right (substring x (match-end 0))))
                        (list (format "%s" (eval (read left)))
                              right)))
                     (t (list x))))))
    (apply 'concat tokens)))

(defun logicless-template:eval-only (string)
  (let ((tokens
         (loop for x in (split-string string "{{{")
               collect
               (cond ((string-match "}}}\n" x)
                      (let ((left (substring x 0 (match-beginning 0)))
                            (right (substring x (match-end 0))))
                        (eval (read left))
                        right))
                     (t x)))))
    (apply 'concat tokens)))

(defun logicless-template:comment (string)
  (let ((tokens
         (loop for x in (split-string string "#|")
               collect
               (cond ((string-match "|#\n" x)
                      (let ((left (substring x 0 (match-beginning 0)))
                            (right (substring x (match-end 0))))
                        (eval (read left))
                        right))
                     (t x)))))
    (apply 'concat tokens)))
  
(defun logicless-template (string)
  (logicless-template:emit
   (logicless-template:eval-only
    (logicless-template:comment string))))
  

(let ((aaa 100))
  (logicless-template "--{{aaa}}--"))
(let ((aaa 100))
  (logicless-template "--{{(+ aaa aaa aaa)}}--"))
(let ((aaa 100))
  (logicless-template "--{{(mapcar (lambda (x) (* aaa x)) '(1 2 3))}}--"))

(let ((aaa 100))
  (logicless-template "--{{
(cond ((= aaa 1000) (+ aaa aaa))
      (t \"fail\"))
}}--"))


(let ((aaa 100))
  (logicless-template "\
{{{
(setq bbb (* aaa aaa))
}}}
#|
this is comment
|#
--{{
(cond ((= aaa 100) (+ bbb aaa))
      (t \"fail\"))
}}--"))