Adding things to unstable/error that are painful to remember and used everywhere

pkgs/unstable-pkgs/unstable-doc/scribblings/error.scrbl

@@ -110,3 +110,9 @@ can be appended to the end of a base error message.
 }
 
 @(close-eval the-eval)
+
+@addition{Jay McCarthy}
+
+@defproc[(exn:not-break? [x any/c]) boolean?]{Identifies values that are not @racket[exn:break?], i.e. values that are safe to catch with @racket[with-handlers].}
+
+@defproc[(error-display [x any/c]) void?]{Calls @racket[(error-display-handler)] with the proper arguments whehter @racket[x] is an exception, or not.}

racket/collects/unstable/error.rkt

@@ -181,3 +181,20 @@ TODO
                [value (cadr lst)])
            (cons (cons field value)
                  (field+detail-list->table who (cddr lst) onto)))]))
+
+;; Added by Jay
+
+(define (exn:not-break? x)
+  (not (exn:break? x)))
+
+(define (error-display x)
+  ((error-display-handler)
+   (if (exn? x)
+     (exn-message x)
+     "non-exn error:")
+   x))
+
+(provide
+ (contract-out
+  [exn:not-break? (-> any/c boolean?)]
+  [error-display (-> any/c void?)]))