News for hackers. Stuff that matters.

A comment on What is type safety?. Parent comment

Re:What is type safety? by tel on Tuesday August 05, 2014 @03:06PM (#8138677)
What happens when a cast is invalid?

You have type-safe casts in Haskell, for instance, where the failure is reflected at runtime.

    cast :: (Typeable a, Typeable b) => a -> Maybe b
Those are alright.
[ Parent | on HN ]
Re:What is type safety? by AnimalMuppet on Tuesday August 05, 2014 @03:24PM (#8138798)
In Java, IIRC, the cast fails with a ClassCastException. That seems to me to be "failure is reflected at runtime".

In C++ with RTTI, IIRC it returns null. That's also "failure at runtime" (of a sort), but you have to check it.

[ Parent | on HN ]
Re:What is type safety? by jeorgun on Tuesday August 05, 2014 @03:39PM (#8138866)
RTTI returns nullptr when casting a pointer, but it does throw an exception when casting references. Both of these behaviors are well-defined, although the first is kind of questionable.
[ Parent | on HN ]