4 ms·

The caller could NOT pass a null value before. Old situation: called function says: "i would crash if you gave me a null value, so my interface says you cannot

The caller could NOT pass a null value before. Old situation: called function says: "i would crash if you gave me a null value, so my interface says you cannot give me a null value" New situation: called function says: "i no longer crash if given a null value, which you couldn't do before anyway, so you won't notice any difference"

tmountain 3y ago
I believe this is exactly what Hickey was arguing.
xmcqdpt2 3y ago
But they could pass null, though. Clojure doesn't stop you from passing null anywhere. Also, thrown exceptions are values. Consider for example a function that searches for a file a return null if it's not found, which you are composing with a function that opens a file but throws on null. You might very well write something like open(search(...)) and catching exceptions above that level. Now if I make open(..) able to accept null (maybe it opens a temp file?) then you now need to add a null check on the return value of search to get the old behaviour. That is 100% a breaking change!
- kybernetikos 3y ago
  But you already had to have a null check on on the return value of search if open wasn't previously able to take null, so the behaviour of your code hasn't changed.
  - xmcqdpt2 3y ago
    Why? You may just have been catching the exception outside both functions. Lots of actual real-life programs, even if it's not the cleanest.
- PaulDavisThe1st 3y ago
  > Clojure doesn't stop you from passing null anywhere As a C++ programmer (oh, the horror!) I'd say that's an issue with Clojure rather than the general principle. And also one of the reasons I like the pointer/reference distinction in C++ (the former allows null values, the latter does not). But sure, that changes my interpretation somewhat. It doesn't really change program safety, however.

4 ms·

The caller could NOT pass a null value before. Old situation: called function says: "i would crash if you gave me a null value, so my interface says you cannot

by PaulDavisThe1st 3y ago

tmountain 3y ago
I believe this is exactly what Hickey was arguing.
xmcqdpt2 3y ago
But they could pass null, though. Clojure doesn't stop you from passing null anywhere. Also, thrown exceptions are values. Consider for example a function that searches for a file a return null if it's not found, which you are composing with a function that opens a file but throws on null. You might very well write something like open(search(...)) and catching exceptions above that level. Now if I make open(..) able to accept null (maybe it opens a temp file?) then you now need to add a null check on the return value of search to get the old behaviour. That is 100% a breaking change!
- kybernetikos 3y ago
  But you already had to have a null check on on the return value of search if open wasn't previously able to take null, so the behaviour of your code hasn't changed.
  - xmcqdpt2 3y ago
    Why? You may just have been catching the exception outside both functions. Lots of actual real-life programs, even if it's not the cleanest.
- PaulDavisThe1st 3y ago
  > Clojure doesn't stop you from passing null anywhere As a C++ programmer (oh, the horror!) I'd say that's an issue with Clojure rather than the general principle. And also one of the reasons I like the pointer/reference distinction in C++ (the former allows null values, the latter does not). But sure, that changes my interpretation somewhat. It doesn't really change program safety, however.