Got new timeslice limiter to work, document.

1 files changed, 10 insertions, 7 deletions

diff --git a/module/srfi/srfi-41/util.scm b/module/srfi/srfi-41/util.scm
index a6c6dc3d..51671985 100644
--- a/module/srfi/srfi-41/util.scm
+++ b/module/srfi/srfi-41/util.scm
@@ -1,8 +1,10 @@
 (define-module (srfi srfi-41 util)
   #:use-module (srfi srfi-1)
   #:use-module (srfi srfi-41)
+  #:use-module ((ice-9 sandbox) :select (call-with-time-limit))
   #:use-module (util) ; let*, find-min
-  #:export (stream-car+cdr interleave-streams with-streams))
+  #:export (stream-car+cdr interleave-streams with-streams
+                           stream-timeslice-limit))
 
 (define (stream-car+cdr stream)
   (values (stream-car stream)
@@ -103,20 +105,21 @@
   (stream-paginate% stream page-size))
 
 
+;; stream cons, but eval arguments beforehand.
 (define (eager-stream-cons a b)
   (stream-cons a b))
 
-(use-modules (ice-9 sandbox) )
-(define (stream-timeslice-limit strm)
+;; Wrap a stream in time limits. Each element has at most @var{timeslice}
+;; seconds to produce a value, otherwise the stream ends. Useful for finding the
+;; "final" element matching a predicate in an infinite stream.
+(define-stream (stream-timeslice-limit strm timeslice)
   (call-with-time-limit
-   0.1
+   timeslice
    (lambda () (eager-stream-cons
           (stream-car strm)
-          (stream-timeslice-limit (stream-cdr strm))))
+          (stream-timeslice-limit (stream-cdr strm) timeslice)))
    (lambda _ stream-null)))
 
-(export stream-timeslice-limit)
-
 ;; Evaluates @var{body} in a context where most list fundamentals are
 ;; replaced by stream alternatives.
 ;; commented defifinitions are items which could be included, but for