Add some utility functions

src/kernel.sl

@@ -142,3 +142,44 @@
 
 (defmacro return (&opt value)
   (list 'return-from nil value))
+
+(defun put (symbol key value)
+  (setplist symbol (plist-set (symbol-plist symbol) key value)))
+
+(defun get (symbol key &opt default)
+  (plist-get (symbol-plist symbol) key default))
+
+(defun remprop (symbol key)
+  (setplist symbol (plist-rem (symbol-plist symbol) key)))
+
+(defmacro dotails (vars &rest body)
+  (let ((cur (make-symbol "cur")))
+    (list 'let (list (list cur (second vars)))
+          (list 'while (list 'pairp cur)
+                (apply 'list 'let (list (list (first vars) cur))
+                       body)
+                (list 'setq cur (list 'tail cur))))))
+
+(defun member (elt list &opt (pred 'equal))
+  (dotails (cur list)
+    (when (funcall pred elt (head cur))
+      (return-from member cur))))
+
+(defun member-if (pred list &opt negate)
+  (dotails (cur list)
+    (when (or (and (not negate) (funcall pred (head cur)))
+              (and negate (not (funcall pred (head cur)))))
+      (return-from member-if cur))))
+
+(defun find (elt list &opt default (pred 'equal))
+  (dolist (cur list)
+    (when (funcall pred cur elt)
+      (return-from find cur)))
+  default)
+
+(defun find-if (pred list &opt default negate)
+  (dolist (cur list)
+    (when (or (and (not negate) (funcall pred cur))
+              (and negate (not (funcall pred cur))))
+      (return-from find-if cur)))
+  default)