7 ms·

> Invariants are functions that run at the start and end of every public member function these are just runtime assertions EDIT: how am i getting downvoted fo

> Invariants are functions that run at the start and end of every public member function these are just runtime assertions EDIT: how am i getting downvoted for copy-pasting literally what the article verifies?

jayd16 1y ago
I think there's something to be said about them running automatically that is lost when you say they're just asserts.
- almostgotcaught 1y ago
  i don't get it - if do int foo(int a) { assert(a > 5); int b = a * 10; assert(b > 50); return b; } do you think those asserts don't "run automatically"?
  - gblargg 1y ago
    You define the invariants once for the class and they are run around every public function. Done manually you'd probably use a helper object that calls the invariants in its constructor and destructor (have to handle exceptions) that you have to add to every public function's definition.
readthenotes1 1y ago
Maybe it's the editorial "just"? Like: software programs can't be that difficult to create properly because they are just 1s and 0s.
- johnisgood 1y ago
  This is not the first time someone getting down-voted for using the word "just". I do not know if this really is warranted, however.
LorenDB 1y ago
Yes, but they are guaranteed to run at the beginning and end. C/C++ asserts need to handle any return path, whereas D has functionality to mark statements to run at the end of any return path while only being written once. See also the scope(exit) feature.
- almostgotcaught 1y ago
  You can accomplish the same exact thing with https://en.cppreference.com/w/cpp/experimental/scope_exit.html https://en.cppreference.com/w/cpp/experimental/scope_exit.ht...
  - WalterBright 1y ago
    The idea for scope-exit came from Andrei Alexandrescu. See https://dlang.org/articles/exception-safe.html https://dlang.org/articles/exception-safe.html He demonstrated it with C++ templates, but the D one is far more straightforward.

jayd16 1y ago

I think there's something to be said about them running automatically that is lost when you say they're just asserts.

almostgotcaught 1y ago
i don't get it - if do int foo(int a) { assert(a > 5); int b = a * 10; assert(b > 50); return b; } do you think those asserts don't "run automatically"?
- gblargg 1y ago
  You define the invariants once for the class and they are run around every public function. Done manually you'd probably use a helper object that calls the invariants in its constructor and destructor (have to handle exceptions) that you have to add to every public function's definition.

readthenotes1 1y ago

Maybe it's the editorial "just"? Like: software programs can't be that difficult to create properly because they are just 1s and 0s.

johnisgood 1y ago
This is not the first time someone getting down-voted for using the word "just". I do not know if this really is warranted, however.

LorenDB 1y ago

Yes, but they are guaranteed to run at the beginning and end. C/C++ asserts need to handle any return path, whereas D has functionality to mark statements to run at the end of any return path while only being written once. See also the scope(exit) feature.

almostgotcaught 1y ago
You can accomplish the same exact thing with https://en.cppreference.com/w/cpp/experimental/scope_exit.html https://en.cppreference.com/w/cpp/experimental/scope_exit.ht...
- WalterBright 1y ago
  The idea for scope-exit came from Andrei Alexandrescu. See https://dlang.org/articles/exception-safe.html https://dlang.org/articles/exception-safe.html He demonstrated it with C++ templates, but the D one is far more straightforward.