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A Fizzy Library Feature with all the Right Buzzwords

Document number: DXXXXR0
Date: 20XX-MM-DD
Audience: LEWG
Reply-to: Tony Van Eerd. tt2 at forecode.com

Summary

Not everything should be in the standard library. Things in the standard library should be one (or hopefully more) of:

  • often needed
  • often implemented
  • hard to get right

FizzBuzz (https://en.wikipedia.org/wiki/Fizz_buzz) checks all the boxes.

Naive FizzBuzz std::fizzbuzz 
struct fb_gen {
  int max = 100;
  generator gen() {
    for (int i:iota(max)) {
      bool f=!(i%3), b=!(i%5);
      co_yield (f?b?"fizzbuzz":"fizz":b?"buzz":to_string(i));
    }
  }
};

int main()
{
  for (auto s : fb_gen{}.gen())
    std::cout << s;
}










int main()
{
  for (auto n : irange(0,100))
    std::cout << std::fizzbuzz(n);
}

Design Considerations

  • efficieny
  • ranges?
  • ease of use
  • include "\n" ?

What About Efficiency

The simple version of std::string fizzbuzz(int); may not be the most efficient. The resulting string will typically fit into the small buffer optimization (SBO), so there is no allocation, but there is still copying.

A more efficient version would likely be:

template<typename F>
std::string fizzbuzz(int n, F & func);

where func gets called like func("fizz")

int main()
{
    for (int i = 1; i <= 100; i++)
    {
        std::fizzbuzz(n, [] (auto s) {
                std::cout << s << '\n';
            });
    }

Q. Does func take char const *, std::string_view, or anything "string-like"?

A: Anything string-like??

Q: Should the non-fizzbuzz numbers be called like func(std::to_string(n) or func(n)?

A: We can check if func(n) is callable with an if constexpr, and call it if true, otherwise convert to string. (And we assume func can take a string-like.)

Open Questions

Unicode? Wide Strings?

Capitalization?

"fizz" or "Fizz" or "FIZZ" or customizable?

Other Languages?

Suggested Votes

The authors thank you for your time, and would appreciate specific directional feedback (in addition to the helpful feedback received during discussion).

Do we want (some form of) std::fizzbuzz?

SF F N A SA
__ __ __ __ __

Do we want std::string std::fizzbuzz(int)?

SF F N A SA
__ __ __ __ __

Do we want max efficient std::fizzbuzz?

SF F N A SA
__ __ __ __ __

etc...

SF F N A SA
__ __ __ __ __

Acknowledgements

@vector_of_bool supplied the (intentionally buggy) "Naive" FizzBuzz.