4 ms·

The issue with languages like C++ is, that you can follow better programming practices, but the compiler doesn't support you in the verification and accordingly

by dan00 14y ago

The issue with languages like C++ is, that you can follow better programming practices, but the compiler doesn't support you in the verification and accordingly you can't trust that easily your code, which complicates the reasoning about a system a lot. Having properties like immutability and pureness in your language makes it lot easier to trust your code and to reason about it.

bad_user 14y ago
Clojure doesn't give you immutability guarantees, it just makes it harder to chose otherwise, but on the other hand calling a Java method on some object is just one special form away. I'm not saying Clojure does the wrong thing here btw, but this thing you're talking about is a fallacy, unless you're working in Haskell and even there you could find ways to screw things up by interacting with the outside world, which isn't immutable.
- dan00 14y ago
  "I'm not saying Clojure does the wrong thing here btw, but this thing you're talking about is a fallacy ..." Please, read exactly. "... unless you're working in Haskell and even there you could find ways to screw things up by interacting with the outside world, which isn't immutable." The whole point is, that you're able to express immutability and pureness in a language like Haskell _AND_ have a compiler which can verify it. You will never be able to prohibit any screwing, but you can make it a lot harder to screw something.
nivertech 14y ago
Erlang: X = 5. X2 = X+1. C++: const int x = 5; const int x2 = x + 1. My C++ style use const modifiers extensively. Likewise you can use final in Java.
- dan00 14y ago
  const_cast and mutable, and gone is any kind of verification.
  - saurik 14y ago
    That your code uses neither is trivially verified with grep. Are you saying your issues would be solved if someone added a ten-line patch to gcc for -Wconst-cast (that provided a waning, obiously upgradable to an error, if you used const_cast; as in, similar to -Wold-style-cast)?
    - dan00 14y ago
      You really can't express immutability and pureness in C++, because you can still modify global variables and do any kind of IO everywhere, regardless of const. const_cast isn't the big issue, because there's also unsafePerformIO in Haskell. For both you could say, that they shouldn't be used, that it's bad programming practice to use them. The point is, even if you follow good programming practices in C++, you can't express them and your compiler can't help you in the verification, if you're really following them. That doesn't might seem like a big thing, it's also not related to your smartness, because it mostly depends on the size and complexity of your system.
      - saurik 14y ago
        If you are arguing that you don't have immutability by default across all values, that is a very different point that I think you need to provide more clarity for... I mean, of course you can modify state that has nothing to do with the variables that are marked const "regardless of const": that is sufficiently obvious as to be a useless comment. However, you really can mark values as const in C++ and allow the compiler to verify that you aren't doing anything non-epic to defeat it. Yes: you can still accidentally or purposefully access the memory via a random hand-calculated pointer, but we can actually harden the compiler (not the language: no changes there required) against that as well by just keeping you from using pointer arithmetic (really, that's a feature that tends to only be used in restricted contexts anyway).
  - deleted 14y ago
    [deleted]

by dan00 14y ago

bad_user 14y ago

Clojure doesn't give you immutability guarantees, it just makes it harder to chose otherwise, but on the other hand calling a Java method on some object is just one special form away. I'm not saying Clojure does the wrong thing here btw, but this thing you're talking about is a fallacy, unless you're working in Haskell and even there you could find ways to screw things up by interacting with the outside world, which isn't immutable.

dan00 14y ago
"I'm not saying Clojure does the wrong thing here btw, but this thing you're talking about is a fallacy ..." Please, read exactly. "... unless you're working in Haskell and even there you could find ways to screw things up by interacting with the outside world, which isn't immutable." The whole point is, that you're able to express immutability and pureness in a language like Haskell _AND_ have a compiler which can verify it. You will never be able to prohibit any screwing, but you can make it a lot harder to screw something.

nivertech 14y ago

Erlang: X = 5. X2 = X+1. C++: const int x = 5; const int x2 = x + 1. My C++ style use const modifiers extensively. Likewise you can use final in Java.

dan00 14y ago
const_cast and mutable, and gone is any kind of verification.
- saurik 14y ago
  That your code uses neither is trivially verified with grep. Are you saying your issues would be solved if someone added a ten-line patch to gcc for -Wconst-cast (that provided a waning, obiously upgradable to an error, if you used const_cast; as in, similar to -Wold-style-cast)?
  - dan00 14y ago
    You really can't express immutability and pureness in C++, because you can still modify global variables and do any kind of IO everywhere, regardless of const. const_cast isn't the big issue, because there's also unsafePerformIO in Haskell. For both you could say, that they shouldn't be used, that it's bad programming practice to use them. The point is, even if you follow good programming practices in C++, you can't express them and your compiler can't help you in the verification, if you're really following them. That doesn't might seem like a big thing, it's also not related to your smartness, because it mostly depends on the size and complexity of your system.
    - saurik 14y ago
      If you are arguing that you don't have immutability by default across all values, that is a very different point that I think you need to provide more clarity for... I mean, of course you can modify state that has nothing to do with the variables that are marked const "regardless of const": that is sufficiently obvious as to be a useless comment. However, you really can mark values as const in C++ and allow the compiler to verify that you aren't doing anything non-epic to defeat it. Yes: you can still accidentally or purposefully access the memory via a random hand-calculated pointer, but we can actually harden the compiler (not the language: no changes there required) against that as well by just keeping you from using pointer arithmetic (really, that's a feature that tends to only be used in restricted contexts anyway).
- deleted 14y ago
  [deleted]