From ad068bc1f86ccc88351e459cd83b4f35c6fa81cf Mon Sep 17 00:00:00 2001
From: Alex Shinn <ashinn@users.noreply.github.com>
Date: Mon, 28 Dec 2009 21:05:25 +0900
Subject: [PATCH] adding srfi-39

---
 lib/srfi/39.module | 25 +++++++++++++++++++++++++
 1 file changed, 25 insertions(+)
 create mode 100644 lib/srfi/39.module

diff --git a/lib/srfi/39.module b/lib/srfi/39.module
new file mode 100644
index 00000000..11b9ed9f
--- /dev/null
+++ b/lib/srfi/39.module
@@ -0,0 +1,25 @@
+
+(define-module (srfi 39)
+  (export make-parameter parameterize)
+  (import-immutable (scheme))
+  (body
+   (define (make-parameter value . o)
+     (if (pair? o)
+         (let ((converter (car o)))
+           (lambda args
+             (if (null? args)
+                 value
+                 (set! value (converter (car args))))))
+         (lambda args (if (null? args) value (set! value (car args))))))
+   (define-syntax parameterize
+     (syntax-rules ()
+       ((parameterize ("step") ((param value tmp1 tmp2) ...) () body)
+        (let ((tmp1 value) ...)
+          (let ((tmp2 (param)) ...)
+            (dynamic-wind (lambda () (param tmp1) ...)
+                          (lambda () . body)
+                          (lambda () (param tmp2) ...)))))
+       ((parameterize ("step") args ((param value) . rest) body)
+        (parameterize ("step") ((param value tmp1 tmp2) . args) rest body))
+       ((parameterize ((param value) ...) . body)
+        (parameterize ("step") () ((param value) ...) body))))))