@@ -93,10 +93,10 @@ operator):

     (== (view lens (set lens value rec))

         value)

- 

+

     (== (set lens (view lens rec) rec)

         rec)

- 

+

     (== (set lens value2 (set lens value1 rec))

         (set lens value2 rec))

@@ -234,11 +234,12 @@ contain the new value at the location focused by the lens."

            #:compress-runs #:combine-matching-lists #:sorted #:applicable-when

            #:of-length #:of-min-length #:of-max-length #:transform-head

            #:maximizing #:zipping #:applying #:splice-elt #:transform-elt #:denest

-           #:op #:defalias #:<> #:<>1))

+           #:op #:defalias #:<> #:<>1

+           #:•))

 (in-package :data-lens)

-(declaim 

+(declaim

  (inline data-lens:over data-lens:transform-tail

          data-lens:applicable-when data-lens:of-min-length

          data-lens:on data-lens:over data-lens:slice

@@ -524,3 +525,5 @@ contain the new value at the location focused by the lens."

 (defmacro <>1 (&rest funs)

   `(alexandria:compose ,@funs))

+(defmacro • (&rest funs)

+  `(alexandria:compose ,@funs))

new file mode 100644

@@ -0,0 +1,53 @@

+(defpackage :data-lens.wrapped-sequence

+  (:use :cl )

+  (:export ))

+(in-package :data-lens.wrapped-sequence)

+

+(defgeneric underlying (wrapper)

+  (:documentation "Return the underlying object of a wrapper"))

+

+(defclass tagged-sequence (standard-object sequence)

+  ((%underlying-sequence :initarg :underlying :accessor underlying)

+   (%key-fn :initarg :key :reader key)

+   (%invert-key :initarg :invert-key :reader invert-key)))

+

+(defmethod sb-sequence:length ((sequence tagged-sequence))

+  (length (underlying sequence)))

+

+(defmethod sb-sequence:elt ((sequence tagged-sequence) index)

+  (funcall (key sequence)

+           (elt (underlying sequence)

+                index)))

+

+(defmethod (setf sb-sequence:elt) (new-value (sequence tagged-sequence) index)

+  (setf (elt (underlying sequence)

+             index)

+        (funcall (invert-key sequence)

+                 (elt (underlying sequence)

+                      index)

+                 new-value)))

+

+(defmethod sb-sequence:adjust-sequence ((sequence tagged-sequence) length

+                                        &rest r

+                                        &key initial-element initial-contents)

+  (declare (ignore initial-element initial-contents))

+  (make-instance 'tagged-sequence

+                 :underlying (apply #'sb-sequence:adjust-sequence

+                                    (copy-seq (underlying sequence)) length

+                                    r)

+                 :key-fn (key sequence)

+                 :invert-key (invert-key sequence)))

+

+(defmethod sb-sequence:make-sequence-like

+    ((sequence tagged-sequence) length &rest r)

+  (apply #'sb-sequence:adjust-sequence sequence length r))

+

+(defun wrap-sequence (seq key-fn invert-key-fn)

+  (if invert-key-fn

+      (make-instance 'tagged-sequence

+                     :underlying seq

+                     :key key-fn

+                     :invert-key invert-key-fn)

+      (make-instance 'tagged-sequence

+                     :underlying seq

+                     :key key-fn)))