From d7dbc7fc8e9c692fe9032d9f7738ffa59498034e Mon Sep 17 00:00:00 2001
From: David Thompson <dthompson2@worcester.edu>
Date: Sat, 6 Dec 2014 11:15:00 -0500
Subject: signal: Add custom record type printer.

* sly/signal.scm: Set record type printer for <signal>.
---
 sly/signal.scm | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/sly/signal.scm b/sly/signal.scm
index 8e150a2..8e2c64d 100644
--- a/sly/signal.scm
+++ b/sly/signal.scm
@@ -24,6 +24,7 @@
 (define-module (sly signal)
   #:use-module (srfi srfi-1)
   #:use-module (srfi srfi-9)
+  #:use-module (srfi srfi-9 gnu)
   #:use-module (srfi srfi-26)
   #:use-module (sly agenda)
   #:use-module (sly coroutine)
@@ -77,6 +78,15 @@
   signal-box?
   (signal signal-unbox signal-box-set!))
 
+;; The user always sees the boxes, so let's hide the underlying
+;; details.
+(set-record-type-printer!
+ <signal-box>
+ (lambda (box port)
+   (let ((signal (signal-unbox box)))
+     (format port "#<signal value: ~a inputs: ~a>"
+             (%signal-ref signal) (signal-inputs signal)))))
+
 ;; Alternate spelling of signal-box? for the public API.
 (define signal? signal-box?)
 
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