DO to DOTIMES

[jscl.git] / src / list.lisp

diff --git a/src/list.lisp b/src/list.lisp
index 58226f8..8efb95a 100644 (file)
--- a/src/list.lisp
+++ b/src/list.lisp
@@ -197,6 +197,14 @@
     (when (eql tail object)
       (return-from tailp t))))
 
+(defun make-list (size &key (initial-element nil))
+  "Create a list of size `size` of `initial-element`s."
+  (when (< size 0)
+    (error "Size must be non-negative"))
+  (let ((newlist))
+    (dotimes (i size newlist)
+      (push initial-element newlist))))
+
 (defun map1 (func list)
   (with-collect
     (while list
@@ -246,11 +254,31 @@
     (setq x (cdr x)))
   x)
 
-(defun butlast (x)
-  (and (consp (cdr x))
-       (cons (car x) (butlast (cdr x)))))
-
-(defun member (x list &key key (test #'eql testp) (test-not #'eql test-not-p)) 
+(defun butlast (x &optional (n 1))
+  "Returns x, less the n last elements in the list."
+  (cond
+      ;; trivial optimizations
+    ((not x) x)
+    ((zerop n) x)
+
+    ;; Base case
+    ((= n 1)
+     (and (consp (cdr x))
+          (cons (car x)
+                (butlast (cdr x) n))))
+    ;; O(n * (length x)) butlast for n > 1.
+    (t
+     (let ((temp x))
+       (do
+        ((iter 0))
+        ;; quit when we reach the top or we ran out
+        ((or (= iter n)
+             (not temp)))
+         (setf temp (butlast temp 1))
+         (incf iter))
+       temp))))
+
+(defun member (x list &key key (test #'eql testp) (test-not #'eql test-not-p))
   (while list
     (when (satisfies-test-p x (car list) :key key :test test :testp testp
                             :test-not test-not :test-not-p test-not-p)
@@ -360,3 +388,51 @@
       (when (member (funcall key x) list2 :test test :key key)
         (push x new-list)))
     new-list))
+
+(defun get-properties (plist indicator-list)
+  (do* ((plist plist (cddr plist))
+        (cdr (cdr plist) (cdr plist))
+        (car (car plist) (car plist)))
+      ((null plist) (values nil nil nil))
+    (when (null cdr)
+      (error "malformed property list ~S" plist))
+    (let ((found (member car indicator-list :test #'eq)))
+      (when found
+        (return (values car (cadr plist) plist))))))
+
+(defun getf (plist indicator &optional default)
+  (do* ((plist plist (cddr plist))
+        (cdr (cdr plist) (cdr plist))
+        (car (car plist) (car plist)))
+      ((null plist) default)
+    (when (null cdr)
+      (error "malformed property list ~S" plist))
+    (when (eq indicator car)
+      (return (cadr plist)))))
+
+(defun %putf (plist indicator new-value)
+  (do* ((tail plist (cddr tail))
+        (cdr (cdr tail) (cdr tail))
+        (car (car tail) (car tail)))
+      ((null tail) (list* indicator new-value plist))
+    (when (null cdr)
+      (error "malformed property list ~S" tail))
+    (when (eq indicator car)
+      ;; TODO: should be cadr, needs a defsetf for that
+      (setf (car (cdr tail)) new-value)
+      (return tail))))
+
+(define-setf-expander getf (plist indicator &optional default)
+  (multiple-value-bind (dummies vals newval setter getter)
+      (get-setf-expansion plist)
+    (let ((store (gensym))
+          (indicator-sym (gensym))
+          (default-sym (and default (gensym))))
+      (values `(,indicator-sym ,@(and default `(,default-sym)) ,@dummies)
+              `(,indicator ,@(and default `(,default)) ,@vals)
+              `(,store)
+              `(let ((,(car newval) (%putf ,getter ,indicator-sym ,store))
+                     ,@(cdr newval))
+                 ,setter
+                 ,store)
+              `(getf ,getter ,indicator-sym ,@(and default `(,default-sym)))))))