1 files changed, 29 insertions, 0 deletions
diff --git a/module/c/line-fold.scm b/module/c/line-fold.scm
new file mode 100644
index 00000000..c61c2c70
--- /dev/null
+++ b/module/c/line-fold.scm
@@ -0,0 +1,29 @@
+(define-module (c line-fold)
+  :use-module (srfi srfi-1)
+  :use-module (srfi srfi-71)
+  :export (fold-lines))
+
+(define (line-continued? line)
+  (and (not (string-null? line))
+       (char=? #\\ (string-ref line (1- (string-length line))))))
+
+(define (strip-backslash line)
+  (string-drop-right line 1))
+
+(define (fold-lines string)
+  (with-output-to-string
+    (lambda ()
+      (let loop ((lines (string-split string #\newline)))
+        (cond ((null? lines) 'NOOP)
+              ((null? (cdr lines))
+               ;; TODO error message if last character is a backslash
+               (display (car lines))
+               (newline))
+              (else
+               (let ((to-merge remaining (span line-continued? lines)))
+                 (for-each display (map strip-backslash to-merge))
+                 (display (car remaining))
+                 (newline)
+                 (for-each (lambda _ (newline))
+                           (iota (length to-merge)))
+                 (loop (cdr remaining)))))))))