diff options
| -rw-r--r-- | racket.html.markdown | 17 |
1 files changed, 11 insertions, 6 deletions
diff --git a/racket.html.markdown b/racket.html.markdown index d3403ff8..4b34fbef 100644 --- a/racket.html.markdown +++ b/racket.html.markdown @@ -375,12 +375,17 @@ m ; => '#hash((b . 2) (a . 1) (c . 3)) <-- no `d' ;;; Exceptions -;; To catch an exception, use the `with-handlers' form -;; To throw an exception use `raise' -(with-handlers - ([(lambda (v) (equal? v "infinity")) - (lambda (exn) +inf.0)]) - (raise "infinity")) +;; To catch exceptions, use the `with-handlers' form +(with-handlers ([exn:fail? (lambda (exn) 999)]) + (+ 1 "2")) ; => 999 +(with-handlers ([exn:break? (lambda (exn) "no time")]) + (sleep 3) + "phew") ; => "phew", but if you break it => "no time" + +;; Use `raise' to throw exceptions or any other value +(with-handlers ([number? ; catch numeric values raised + identity]) ; return them as plain values + (+ 1 (raise 2))) ; => 2 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; ;; 6. Mutation |