What C++ idioms should C++ programmers use?

Question

What C++ idioms should C++ programmers know?

By C++ idioms, I mean design patterns or way of doing certain things that are only applicable for C++ or more applicable for C++ than most other languages.

Why one should use the idioms, and what do the idioms accomplish?

Answer 1

Here is one list. If I had to pick a couple I might go with the Curiously Recurring Template Pattern or Virtual Contstructors.

Answer 2

PIMPL, aka P ointer to IMPL ementation ?

Answer 3

By far the single most important "pattern" to learn and know that's (nearly) unique to C++ is RAII (Resource Acquisition Is Initialization).

Edit: (To answer extra question edited into the question). You use RAII primarily to (semi-)automate resource management. The most obvious use is freeing resources owned by objects when the owning objects go out of scope, such as freeing memory or closing files.

Answer 4

Template metaprogramming. It's great because it's basically compile-time duck typing, so you get most of the flexibility of duck typing with the speed of static typing.

Answer 5

If you want to get the most out of the STL then iterators and functors/function objects are essential idioms. The use of iterators also implicitly relies on the 'half-open range' idiom too.

Answer 6

RAII, COW, pimpl, law of demeter (not sure if can be classified as idiom), type traits and policies. (COW and law of demeter are not limited to C++ though)

Answer 7

Exploiting Strong Typing and const correctness is also extremely helpful.

I also prohibit default copy constructors and assignment operators. I actually go beyond that, but those are the most common. I think life would be easier if they were not implicit.