From 9dc66f01d3116e663627c9e9f15a0de60035a246 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Hugo=20H=C3=B6rnquist?= <hugo@lysator.liu.se>
Date: Thu, 21 Mar 2019 02:37:54 +0100
Subject: Started work on stream interleaving.

---
 srfi/srfi-41/util.scm | 24 ++++++++++++++++++++++++
 1 file changed, 24 insertions(+)
 create mode 100644 srfi/srfi-41/util.scm

(limited to 'srfi')

diff --git a/srfi/srfi-41/util.scm b/srfi/srfi-41/util.scm
new file mode 100644
index 00000000..ed378ea4
--- /dev/null
+++ b/srfi/srfi-41/util.scm
@@ -0,0 +1,24 @@
+(define-module (srfi srfi-41 util)
+  #:use-module (srfi srfi-1)
+  #:use-module (srfi srfi-41)
+  #:use-module (util) ; let*, find-min
+  #:export (stream-car+cdr interleave-streams))
+
+(define (stream-car+cdr stream)
+  (values (stream-car stream)
+          (stream-cdr stream)))
+
+;; Merges a number of totally ordered streams into a single
+;; totally ordered stream.
+;; ((≺, stream)) → (≺, stream)
+(define (interleave-streams < streams)
+  ;; Drop all empty streams
+  (let ((streams (remove stream-null? streams)))
+    ;; If all streams where empty, end the output stream
+    (if (null? streams)
+        stream-null
+        (let* ((min other (find-min < stream-car streams))
+               (m ms (stream-car+cdr min)))
+          (stream-cons m (interleave-streams < (cons ms other)))))))
+
+;;; Varför är allting så långsamt‽‽‽‽‽‽‽‽
-- 
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