std::string formatting like sprintf

Question

I have to format std::string with sprintf and send it into file stream. How can I do this?

Answer 1

C++20 std::format

It has arrived! The feature is described at: http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2019/p0645r9.html and uses a Python-like .format() syntax.

I expect that the usage will be like:

#include 
#include 

int main() {
    std::string message = std::format("The answer is {}.", 42);
}

I'll give it a try when support arrives to GCC, GCC 9.1.0 with g++-9 -std=c++2a still doesn't support it.

The API will add a new std::format header:

The proposed formatting API is defined in the new header and should have no impact on existing code.

The existing fmt library claims to implement it if you need the polyfill: https://github.com/fmtlib/fmt

Implementation of C++20 std::format.

and was previously mentioned at: std::string formatting like sprintf

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