Merge pull request #7 from odanoburu/master

OS-dependent view-result function

quad/quadwriter/lang-helper.rkt

@@ -34,8 +34,13 @@
               (define DOC (DOC-PROC (list . EXPRS)))
               (define pdf-path (path-string->pdf-path 'PATH-STRING))
               (define (VIEW-RESULT)
+                (define open-string
+                  (case (system-type 'os)
+                    ('macosx "open ~a")
+                    ('unix   "xdg-open ~a &> /dev/null")
+                    (else (error "Don't know how to open PDF file."))))
                 (when (file-exists? pdf-path)
-                  (void (system (format "open ~a" pdf-path)))))
+                  (void (system (format open-string pdf-path)))))
               (module+ main
                 (render-pdf DOC pdf-path))))]))))