Changes between Version 6 and Version 7 of WikiStart

Timestamp:

08/14/24 14:17:22 (9 months ago)

Author:

Enrico Schwass

Comment:

--

WikiStart

@@ -127 +127 @@
 
 This code takes a list of lists and splits it into separate groups whenever a sublist starts with the specified symbol. Each group is then added to the result. The result is a list of these grouped sublists.
+
+To solve this problem in Scheme recursively, let's define a recursive function that will process the list of lists and split them into groups whenever a sublist starts with the specified symbol.
+
+### Steps:
+
+1. **Base Case**: If the list of lists is empty, return an empty list.
+2. **Recursive Case**: 
+    - If the first sublist starts with the given symbol and the current group is not empty, start a new group.
+    - Otherwise, continue adding sublists to the current group.
+
+### Scheme Implementation:
+
+Here’s how you can implement this in Scheme:
+
+```scheme
+(define (split-list-of-lists list-of-lists symbol)
+  (define (split-helper lists current-group result)
+    (cond
+      ((null? lists) 
+       (if (null? current-group) 
+           result
+           (append result (list current-group))))
+      ((equal? (caar lists) symbol)
+       (if (null? current-group)
+           (split-helper (cdr lists) (list (car lists)) result)
+           (split-helper (cdr lists) (list (car lists)) (append result (list current-group)))))
+      (else
+       (split-helper (cdr lists) (append current-group (list (car lists))) result))))
+  (split-helper list-of-lists '() '()))
+
+;; Example usage:
+(define list-of-lists 
+  '((a 1 2 3)
+    (b 4 5 6)
+    (* 7 8 9)
+    (c 10 11)
+    (* 12 13)
+    (d 14 15 16)))
+
+(define symbol '*)
+
+(split-list-of-lists list-of-lists symbol)
+```
+
+### Explanation:
+
+1. **`split-list-of-lists`**: The main function that initializes the recursive process with an empty `current-group` and `result`.
+
+2. **`split-helper`**: 
+    - **Base Case**: When `lists` is empty, if `current-group` is also empty, return the `result`. Otherwise, append the `current-group` to the `result`.
+    - **When symbol is encountered**: If the current group is not empty, append it to the result and start a new group. If the current group is empty, simply start a new group with the current sublist.
+    - **Else case**: Append the current sublist to the `current-group` and continue the recursion.
+
+### Example Output:
+Running the above code with the example `list-of-lists` and `symbol`, you should get:
+
+```scheme
+'(((a 1 2 3) (b 4 5 6)) 
+  ((* 7 8 9) (c 10 11)) 
+  ((* 12 13) (d 14 15 16)))
+```
+
+This Scheme code recursively processes the list of lists and splits them into groups based on the given symbol.
+