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authorColin Okay <colin@cicadas.surf>2022-10-22 08:26:16 -0500
committerColin Okay <colin@cicadas.surf>2022-10-22 08:26:16 -0500
commit5d1ce10ec8f041d7b25c27363620b7db63dff19b (patch)
treea46f4f6ef85bb797939188e7174b1d04bd94584e /utilities.lisp
parent16e1a142a28a0421bc91456ca7bf4cac6a14095f (diff)
Add: utility modules
Diffstat (limited to 'utilities.lisp')
-rw-r--r--utilities.lisp53
1 files changed, 53 insertions, 0 deletions
diff --git a/utilities.lisp b/utilities.lisp
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+;;;; utilities.lisp
+
+(in-package #:vampire)
+
+(let ((host (uiop:hostname))
+ (count 0))
+ (defun nuid ()
+ "Generates a Nearly Universal ID"
+ (format nil "~36r"
+ (sxhash
+ (list
+ (incf count)
+ host
+ (get-universal-time))))))
+
+(defun take (n list &key share-tail)
+ "Returns two values. The first value returned is a list of the first
+ N members of LIST. The second value is a list of the remaining
+ values of list.
+
+ If N is negative, NIL is returned for both values. If N is greater
+ than the length of LIST then the entire list is returned.
+
+ If SHARE-TAIL is non-nil, the second value will
+ share memory with LIST, otherwise a copy is returned."
+ (if (zerop n)
+ (values nil (if share-tail list (copy-seq list)))
+ (loop repeat n
+ for (h . tail) on list
+ collect h into front
+ finally
+ (return (values front
+ (if share-tail
+ tail
+ (copy-seq tail)))))))
+
+(defun insert-nth (x n list)
+ "Creates a new list, the result of inserting X into the Nth position
+ of LIST, displacing the rest of the elements by one position. If N
+ is greater than the length of LIST, X becomes the last element of
+ LIST. If N is negative, a list containing just X is returned."
+ (multiple-value-bind (front back) (take n list)
+ ;; NCONC ok b/c this call to TAKE returns values that do not shre
+ ;; memory with LIST
+ (nconc front (cons x back))))
+
+(defun nswap (list n m)
+ "Swap Nth and Mth members of LIST. Mutates LIST. Assumes both N and
+ M are less than the length of LIST."
+ (let ((tmp (nth n list)))
+ (setf (nth n list) (nth m list)
+ (nth m list) tmp)
+ list))