Standalone Text Formatting Library

This is a simple library for text formatting in C++. It is inspired by (but not compatible to) std::format and {fmt}. Please make sure that your compiler supports at least C++20. That's GCC 10 or Clang 13.

How to use this library in your program.

Just copy the safmat.hpp file into your projects include directory. Alternatively you can install it into /usr/local/include. Then you should be able to #include "safmat.hpp" the file and use it.

HowTo Enable/Disable features.

Just #define the following to 0 or 1, before #includeing the file.

• SAFMAT_OUT_OSTREAM (std::ostream& OutputIterator)
• SAFMAT_OUT_FILE (FILE* OutputIterator)

Examples

1. Getting started

#include "safmat.hpp"

int main() {
    safmat::println("Hello {}!", "World");
}

2. Implementing your own Formatter

<--snip-->
struct Person {
    std::string name;
    unsigned int age;
};

template<>
struct safmat::Formatter<Person> {
    char rep{'s'};  // s=simple x=extended
    
    void parse(safmat::InputIterator &in) {
        switch (*in) {
        case 's':
        case 'x':
            rep = *in++;
            break;
        case '}':
            return;
        default:
            throw safmat::format_error{"Invalid format specifier."};
        }
    }
    
    void format_to(safmat::FormatContext &ctx, const Person &p) {
        auto &out = ctx.out;
        
        switch (rep) {
        case 's':
            safmat::format_to(out, "{}", p.name);
            break;
        case 'x':
            safmat::format_to(out, "Person{{ name=\"{}\", age={} }}", p.name, p.age);
            break;
        default:
            throw safmat::format_error{"Unimplemented format specifier."};
        }
    }
};

int main() {
    Person p{"Max Mustermann", 42};
    safmat::println("p = {}", p);
}

3. Implementing your own OutputAdapter

<--snip-->
template<>
struct safmat::io::OutputAdapter<std::vector<char>> {
    inline static void write(std::vector<char> *vec, std::string_view s) {
        vec->insert(end(*vec), begin(s), end(s));
    }
};

int main() {
    std::vector<char> chars{};
    safmt::print(chars, "Hello World {}", 42);
    
    safmat::println("{}", chars);
}

For more examples look into test.cpp.

TODO

• Implement more Formatter<> specializations.
  • std::floating_point
  • std::chrono::*
  • std::pair
  • std::tuple (maybe?)
  • T*
• Implement more standard format specifiers and do it properly
• Implement a way to do nested arguments (eg. "{:0{}x}").
• Replace OutputIterator with something different.
• Somehow make the library char-independent without templating vformat_to().
• vformat()
• vprint(), vprintln()
• (maybe) implement locale-specific stuff (probably not)
• Make the library constexpr (requires C++23's constexpr unique_ptr)