The in/out features come into their own when inheritance is in play, i.e. for member functions of classes and interfaces. See https://dlang.org/spec/function.html#in_out_inheritance

`import` is so cool we extended it to be able to import .c files! The D compiler internally translates them to D so they can be used. When this was initially proposed, the reaction was "what's that good for?" It turned out to be incredibly useful and a huge time saver.

The concept is sort of like C++ being a superset of C and so being able to incorporate C code, except unlike C++, the C syntax can be left behind. After all, don't we get tired of:

    struct Tag { ... } Tag;

?

▲ 1718627440 a day ago | parent [-]

> struct Tag { ... } Tag;

What's the thing with the syntax? If you don't intend to use the type elsewhere don't give it a tag, if you want, you have to give it a name. (Assuming you are annoyed by the duplicate Tag)

	▲	WalterBright 36 minutes ago \| parent [-]
		Which would you prefer: `struct Tag { ... }` or: `typedef struct Tag { ... } Tag;` ? It's just simpler and easier to write code in D than in C/C++. For another example, in C/C++: `int foo(); int bar() { return foo(); } int foo() { return 3; }` The D equivalent: `int bar() { return foo(); } int foo() { return 3; }`