substr-rope

Author: garlic0x1

README.md

@@ -22,6 +22,9 @@ With [Ultralisp](https://ultralisp.org/) installed:
 Convert a string to a rope with `make-rope`, and turn it back into a
 string with `write-rope` passing `nil` as the output.
 
+You can also pass an input stream or pathname to `make-rope` to
+efficiently read files.
+
 ```lisp
 (let* ((rope (rope:make-rope "Immutable Ropes for Common Lisp"))
        (super (rope:insert-rope rope 10 "Super "))
@@ -32,7 +35,7 @@ string with `write-rope` passing `nil` as the output.
    (rope:write-rope superer nil)))
 ```
 
-Split a rope at an index
+Split a rope at an index:
 
 ```lisp
 (let ((rope (rope:make-rope "Immutable Super Ropes for Common Lisp")))
@@ -56,6 +59,21 @@ Concatenate ropes together:
 
 ![Concatenated Rope](screenshots/concat.png)
 
+Kill a segment of a rope:
+
+```lisp
+(let ((rope (rope:make-rope "Immutable Ropes for Common Lisp")))
+  (rope:write-rope (rope:kill-rope rope 20 27) t))
+```
+
+Get chars or strings at a position:
+
+```lisp
+(let ((rope (rope:make-rope "Immutable Ropes for Common Lisp")))
+  (print (rope:index-rope rope 2))
+  (print (rope:substr-rope rope 10 15)))
+```
+
 # Dev Utils
 
 If you want to generate graphs as shown above, you will need to

package.lisp

@@ -3,18 +3,13 @@
   (:export
    #:rope                               ; CLASS
    #:rope-length                        ; ACCESSOR
-   #:rope-depth                         ; ACCESSOR
-   #:branch                             ; CLASS
-   #:branch-left                        ; ACCESSOR
-   #:branch-right                       ; ACCESSOR
-   #:leaf                               ; CLASS
-   #:leaf-string                        ; ACCESSOR
    #:make-rope                          ; CONSTRUCTOR
    #:write-rope                         ; FUNCTION
    #:prepend-rope                       ; FUNCTION
    #:append-rope                        ; FUNCTION
    #:insert-rope                        ; FUNCTION
    #:index-rope                         ; FUNCTION
+   #:substr-rope                        ; FUNCTION
    #:concat-rope                        ; FUNCTION
    #:split-rope                         ; FUNCTION
    #:kill-rope                          ; FUNCTION

rope.lisp

@@ -180,6 +180,14 @@
           (index-rope (branch-left rope) index)
           (index-rope (branch-right rope) (- index weight))))))
 
+(defun substr-rope (rope from &optional to)
+  "Get a substring out of a rope."
+  (multiple-value-bind (ante _) (split-rope rope (or to (rope-length rope)))
+    (declare (ignore _))
+    (multiple-value-bind (_ post) (split-rope ante from)
+      (declare (ignore _))
+      (write-rope post nil))))
+
 ;;--------;;
 ;; Concat ;;
 ;;--------;;

test/basic.lisp

@@ -41,10 +41,13 @@ can be done efficiently.")
     (is (string= "Hello, super rope!" (rope:write-rope super nil)))))
 
 (deftest index-rope ()
-  "Test accessing characters by index"
+  "Test accessing characters and strings by index"
   (let* ((rope (rope:make-rope "0123456789")))
     (is (string= #\1 (rope:index-rope rope 1)))
-    (is (string= #\9 (rope:index-rope rope 9)))))
+    (is (string= #\9 (rope:index-rope rope 9))))
+  (let ((rope (rope:make-rope "Immutable Ropes for Common Lisp")))
+    (is (string= "Ropes" (rope:substr-rope rope 10 15)))))
+
 
 (deftest read-files-and-streams ()
   "Test reading a file to a rope."