David Bowie

1 files changed, 58 insertions, 0 deletions

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+;;; elephant.el --- Remember variables and modes -*- lexical-binding: t; -*-
+
+;;; Code:
+
+(defmacro elephant-remember (alist)
+  "Setup a closure remembering symbols to apply with
+`remember-reset'.  The variables will be renamed using TEMPLATE.
+ALIST contains cells of the form (SYMBOL . NEW-VALUE), where
+SYMBOL is a variable or mode name, and its value is what to set
+after `remember-set'."
+  (unless lexical-binding
+    (user-error "`elephant' requires lexical binding."))
+
+  (let* ((template (format "elephant--%s-%%s" (gensym)))
+         (reset-fn (intern (format template "reset"))))
+    (cl-destructuring-bind (let-list fn-set-list fn-reset-list)
+        (cl-loop
+         for (sym . val) in (if (symbolp alist) (symbol-value alist) alist)
+         as rem = (intern (format template sym))
+
+         collect (list rem sym)
+         into let-list
+
+         collect (cond ((eq val 'enable)
+                        `(,sym +1))
+                       ((eq val 'disable)
+                        `(,sym -1))
+                       (t `(setq-local ,sym ,val)))
+         into fn-set-list
+
+         collect (cond ((memq val '(enable disable))
+                        `(progn (,sym (if ,rem +1 -1))
+                                (fmakunbound ',rem)))
+                       (t `(progn (setq-local ,sym ,rem)
+                                  (makunbound ',rem))))
+         into fn-reset-list
+
+         finally return (list let-list
+                              fn-set-list
+                              fn-reset-list))
+      `(progn
+         (defvar-local ,reset-fn nil
+           "Function to recall values from `elephant-remember'.")
+         (let ,let-list
+           (setf (symbol-function ',reset-fn)
+                 (lambda ()
+                   ,@fn-reset-list
+                   (redraw-display)
+                   (fmakunbound ',reset-fn))))
+         ,@fn-set-list
+         ',reset-fn))))
+
+(defun elephant-forget ()
+  "Forget all symbols generated by `elephant-remember'."
+  )
+
+(provide 'elephant)
+;;; elephant.el ends here