X-Git-Url: https://thelambdalab.xyz/gitweb/index.cgi?p=sam.git;a=blobdiff_plain;f=fifo.scm;h=ca5634fac28bd1e07ec63d750a229783c6aab4ec;hp=ab5eda05a5e6e22c945ac83d6f0241746e07c966;hb=HEAD;hpb=bf8a20a40dd9e5d963498a0fe43ef5fea52d07c6

diff --git a/fifo.scm b/fifo.scm
index ab5eda0..ca5634f 100644
--- a/fifo.scm
+++ b/fifo.scm
@@ -1,7 +1,11 @@
+;;; A basic FIFO queue module.
+;;;
+
 (module fifo
     (make-fifo
      fifo-push
      fifo-pop
+     fifo-empty?
      fifo->list)
 
   (import scheme
@@ -38,6 +42,7 @@
                  (set! head '())
                  (set-cell-next! tail '()))
              (cell-val old-tail)))
+          ((empty?) (null? head))
           ((->list)
            (let loop ((this-cell head))
              (if (null? this-cell)
@@ -51,5 +56,8 @@
   (define (fifo-pop fifo)
     (fifo 'pop))
 
+  (define (fifo-empty? fifo)
+    (fifo 'empty?))
+
   (define (fifo->list fifo)
     (fifo '->list)))