On Saturday, April 14, 2012 07:41:33 F i L wrote: > > You're supposed to initialize them or assign them > > to appropriate values before using them. > > sure, but if they always default to _usable_ constants no > expectations are lost and no bugs are created.
No. You always have a bug if you don't initialize a variable to the value that it's supposed to be. It doesn't matter whether it's 0, NaN, 527.1209823, or whatever. All having a default value that you're more likely to use means is that you're less likely to have to explicitly initialize the variable. It has to be initialized to the correct value regardless. And if you're in the habit of always initializing variables and never relying on the defaults if you can help it, then the cases where variables weren't initialized to what they were supposed to be stand out more. > > but the whole purpose of default initialization is to make code > > fail > > deterministically when variables aren't properly initialized - > > and to fail as > > quickly as possible. > > that only makes sense in C/C++ where value are implicitly garbage > and mess things up. ??? D was designed with an eye to improve on C/C++. In C/C++, variables aren't guaranteed to be initialized, so if you forget to initialize them, you get garbage, which is not only buggy, it results in non-deterministic behavior. It's always a bug to not initialize a variable. D's approach is to say that it's _still_ a bug to not initialize a variable, since you almost always need to initialize a variable to something _other_ than a default. But rather than leaving them as garbage, D makes it so that variables are default-initialized, making the buggy behavior deterministic. And since not initializing a variable is almost always a bug, default values which were the closest to error values for each type were chosen. You can disagree with the logic, but there it is. I don't see how it's an issue, since you almost always need to initialize variables to something other than the default, and so leaving them as the default is almost always a bug. The only point of dispute that I see in general is whether it's better to rely on the default or to still explicitly initialize it when you actually want the default. Relying on the default works, but by always explicitly initializing variables, those which are supposed to be initialized to something other than the defaults but aren't are then much more obvious. Regardless, the _entire_ reason for default-initialization in D revolves around making buggy initializations deterministic and more detectable. - Jonathan M Davis
