initial

context.zp

@@ -0,0 +1,21 @@
+(define-syntax with
+  (syntax-rules
+    "use a context manager. Takes a value, name and body
+     and binds value to name in body. Ensures resource cleanup.
+
+     params:
+      - val: the value to bind
+      - var: the name to bind to
+      - body: varargs for the body
+     complexity: O(1)
+     returns: the result of the resource cleanup"()
+    ((_ val var body ...)
+      (let ((var val))
+        (begin
+          body ...
+          (teardown var))))))
+
+(defprotocol context-manager ((teardown 1)))
+(defimpl context-manager input-port?  ((teardown close-input-file)))
+(defimpl context-manager output-port? ((teardown close-output-file)))
+(defimpl context-manager net:socket? ((teardown net:close-socket)))