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:
- Base Case: If the list of lists is empty, return an empty list.
- 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:
(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:
split-list-of-lists
: The main function that initializes the recursive process with an emptycurrent-group
andresult
.
split-helper
:- Base Case: When
lists
is empty, ifcurrent-group
is also empty, return theresult
. Otherwise, append thecurrent-group
to theresult
. - 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.
- Base Case: When
### Example Output:
Running the above code with the example list-of-lists
and symbol
, you should get:
'(((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.