4 ms·

The question is how to do automatic resource management. There are no checks of any sort, runtime or not, to help you here (correct me if I'm wrong). RAII is n

The question is how to do automatic resource management. There are no checks of any sort, runtime or not, to help you here (correct me if I'm wrong). RAII is not precluded by explicitness, you could require all values that require cleanup to be syntactically marked in some way and it would still be RAII. defer also cannot handle resources whose lifetimes do not correspond to nested scopes (eg. the elements of an ArrayList) like RAII or a GC can.

pron 6y ago
> RAII is not precluded by explicitness, you could require all values that require cleanup to be syntactically marked in some way and it would still be RAII. I think this one is TBD. > defer also cannot handle resources whose lifetimes do not correspond to nested scopes (eg. the elements of an ArrayList) like RAII or a GC can. Yep, defer won't work if there is no known lifetime scope, but I think this one is actually a good tradeoff to make in a low-level language. Don't get me wrong -- I love tracing GCs and think that they're the right choice for the vast majority of application software, plus there have been great strides made in GC capabilities in the past few years, but in the domains where low-level languages are appropriate there is a different set of constraints. Low-level programming is not like high-level programming, and IMO it's wrong to even try to make them look alike.
int_19h 6y ago
> defer also cannot handle resources whose lifetimes do not correspond to nested scopes It can, it's just more explicit about it. In a language with destructors, you'd do RAII here by having a list destructor that cleans up each element in turn. In a language with defer, the same destructor becomes a regular function that you'd invoke in the deferred expression.
- deleted 6y ago
  [deleted]
- edflsafoiewq 6y ago
  The issue is with the individual elements, which get pushed to the list, popped off the list, moved around, pushed to a different list, etc. The other issue is since there is no generic notion of a destructor, it isn't possible to write generic functions that destroy elements. If you call, say, replace_range on a list of strings, it will leak the replaced strings.
  - int_19h 6y ago
    > The issue is with the individual elements, which get pushed to the list, popped off the list, moved around, pushed to a different list, etc. That's separate from the destructor for the entire list. It does mean that the code that removes an element from the list has to explicitly invoke the destructor for it - which is in agreement with using "defer" to explicitly invoking destructors for locals. > The other issue is since there is no generic notion of a destructor, it isn't possible to write generic functions that destroy elements. But you can have a generic notion of a destructor - that's orthogonal to whether destructors are invoked explicitly. You just have an interface (or trait, or whatever it's called) that exposes a destructor method for a type.
    - edflsafoiewq 6y ago
      You could but Zig does not.

pron 6y ago

> RAII is not precluded by explicitness, you could require all values that require cleanup to be syntactically marked in some way and it would still be RAII. I think this one is TBD. > defer also cannot handle resources whose lifetimes do not correspond to nested scopes (eg. the elements of an ArrayList) like RAII or a GC can. Yep, defer won't work if there is no known lifetime scope, but I think this one is actually a good tradeoff to make in a low-level language. Don't get me wrong -- I love tracing GCs and think that they're the right choice for the vast majority of application software, plus there have been great strides made in GC capabilities in the past few years, but in the domains where low-level languages are appropriate there is a different set of constraints. Low-level programming is not like high-level programming, and IMO it's wrong to even try to make them look alike.

int_19h 6y ago

> defer also cannot handle resources whose lifetimes do not correspond to nested scopes It can, it's just more explicit about it. In a language with destructors, you'd do RAII here by having a list destructor that cleans up each element in turn. In a language with defer, the same destructor becomes a regular function that you'd invoke in the deferred expression.

deleted 6y ago
[deleted]
edflsafoiewq 6y ago
The issue is with the individual elements, which get pushed to the list, popped off the list, moved around, pushed to a different list, etc. The other issue is since there is no generic notion of a destructor, it isn't possible to write generic functions that destroy elements. If you call, say, replace_range on a list of strings, it will leak the replaced strings.
- int_19h 6y ago
  > The issue is with the individual elements, which get pushed to the list, popped off the list, moved around, pushed to a different list, etc. That's separate from the destructor for the entire list. It does mean that the code that removes an element from the list has to explicitly invoke the destructor for it - which is in agreement with using "defer" to explicitly invoking destructors for locals. > The other issue is since there is no generic notion of a destructor, it isn't possible to write generic functions that destroy elements. But you can have a generic notion of a destructor - that's orthogonal to whether destructors are invoked explicitly. You just have an interface (or trait, or whatever it's called) that exposes a destructor method for a type.
  - edflsafoiewq 6y ago
    You could but Zig does not.