Why is the use of tuples in C++ not more common?

Question

Why does nobody seem to use tuples in C++, either the Boost Tuple Library or the standard library for TR1? I have read a lot of C++ code, and very rarely do I see the use of tup

Answer 1

Because it's not yet standard. Anything non-standard has a much higher hurdle. Pieces of Boost have become popular because programmers were clamoring for them. (hash_map leaps to mind). But while tuple is handy, it's not such an overwhelming and clear win that people bother with it.

Answer 2

For me, it's habit, hands down: Tuples don't solve any new problems for me, just a few I can already handle just fine. Swapping values still feels easier the old fashioned way -- and, more importantly, I don't really think about how to swap "better." It's good enough as-is.

Personally, I don't think tuples are a great solution to returning multiple values -- sounds like a job for structs.

Answer 3

As a data-store std::tuple has the worst characteristics of both a struct and an array; all access is nth position based but one cannot iterate through a tuple using a for loop.

So if the elements in the tuple are conceptually an array, I will use an array and if the elements are not conceptually an array, a struct (which has named elements) is more maintainable. ( a.lastname is more explanatory than std::get<1>(a)).

This leaves the transformation mentioned by the OP as the only viable usecase for tuples.

Answer 4

A cynical answer is that many people program in C++, but do not understand and/or use the higher level functionality. Sometimes it is because they are not allowed, but many simply do not try (or even understand).

As a non-boost example: how many folks use functionality found in <algorithm>?

In other words, many C++ programmers are simply C programmers using C++ compilers, and perhaps std::vector and std::list. That is one reason why the use of boost::tuple is not more common.

Answer 5

Certainly tuples can be useful, but as mentioned there's a bit of overhead and a hurdle or two you have to jump through before you can even really use them.

If your program consistently finds places where you need to return multiple values or swap several values, it might be worth it to go the tuple route, but otherwise sometimes it's just easier to do things the classic way.

Generally speaking, not everyone already has Boost installed, and I certainly wouldn't go through the hassle of downloading it and configuring my include directories to work with it just for its tuple facilities. I think you'll find that people already using Boost are more likely to find tuple uses in their programs than non-Boost users, and migrants from other languages (Python comes to mind) are more likely to simply be upset about the lack of tuples in C++ than to explore methods of adding tuple support.

Answer 6

When using C++ on embedded systems, pulling in Boost libraries gets complex. They couple to each other, so library size grows. You return data structures or use parameter passing instead of tuples. When returning tuples in Python the data structure is in the order and type of the returned values its just not explicit.