par: piece-table: some utilities for functional approach

1 files changed, 21 insertions, 0 deletions

diff --git a/par/piece-table.scm b/par/piece-table.scm
index 54cb9a9..f5f58da 100644
--- a/par/piece-table.scm
+++ b/par/piece-table.scm
@@ -213,6 +213,10 @@
        (values piece rem))
       (else
        (loop (piece-next piece) (- rem (piece-length piece)))))))
+
+(define (piece-table-last-piece piece-table)
+  (piece-prev (piece-prev (piece-table-piece piece-table))))
+
 
 
 
@@ -231,10 +235,25 @@
       (+ acc (piece-length piece))
       (loop (piece-next piece) (+ (piece-length piece) acc)))))
 
+(define (%piece-fold-from piece f identity)
+  (let loop ((piece piece)
+             (acc   identity))
+    (unless (sentinel-piece? piece)
+      (loop (piece-next piece) (f piece acc)))))
+
+(define (%piece-fold-from-right piece f identity)
+  (let loop ((piece piece)
+             (acc  identity))
+    (unless (sentinel-piece? piece)
+      (loop (piece-prev piece) (f piece acc)))))
+
+
 (define (piece-table-for-each piece-table f from to)
   ;; TODO: default from and to
   ;; TODO: maybe combine with the `piece-table-index->piece+index` to find the
   ;; `from`
+  ;; TODO: make this lower level, searching from a piece, not from the table
+  ;; TODO: implement using `%piece-fold-from`
   "Calls `f` through the characters of the piece-table, like `string-for-each`
   would do, but the `f` call also includes the piece (to expose extra data) and
   the index of the character"
@@ -265,6 +284,7 @@
   "-right version of piece-table-for-each, it finds the tail and goes
   backwards"
   ;; TODO: not implemented yet
+  ;; TODO: make this lower level, searching from a piece, not from the table
   )
 
 
@@ -330,6 +350,7 @@
 
 (define (piece-table-find piece-table char from)
   ;; TODO: generalize the from
+  ;; TODO: Implement the backwards one too
   (call/cc (lambda (cont)
              (piece-table-for-each
                piece-table