1 files changed, 15 insertions, 6 deletions

@@ -113,17 +113,26 @@
          (eval sym (interaction-environment))
          #t)))))
 
-(define (displayed x)
+(define (with-output-to-string thunk)
   (call-with-port (open-output-string)
     (lambda (port)
-      (display x port)
+      (parameterize ((current-output-port port))
+        (thunk))
       (get-output-string port))))
 
-(define (written x)
-  (call-with-port (open-output-string)
+(define (with-input-from-string s thunk)
+  (call-with-port (open-input-string s)
     (lambda (port)
-      (write x port)
-      (get-output-string port))))
+      (parameterize ((current-input-port port))
+        (thunk)))))
+
+(define (displayed x)
+  (with-output-to-string
+    (lambda () (display x))))
+
+(define (written x)
+  (with-output-to-string
+    (lambda () (write x))))
 
 (define (print . xs)
   (for-each display xs)