Skip to content
Branch: master
Find file Copy path
Find file Copy path
Fetching contributors…
Cannot retrieve contributors at this time
50 lines (37 sloc) 2.33 KB


Small, safe and fast formatting library C++ Format (cppformat) packaged into a CinderBlock.


// Python-like format string syntax:
std::string s = fmt::format("The answer is {}", 42);
// s == "The answer is 42"

// Arguments can be accessed by position and arguments' indices can be repeated:
std::string s = fmt::format("{0}{1}{0}", "abra", "cad");
// s == "abracadabra"

// printf-like numeric formatting:
std::string s = fmt::format("π {:.2f}", 3.1415926535f);
// s == "π 3.14"

// Errors in format strings are reported via exceptions to prevent buffer overflows:
std::string s = fmt::format("The answer is {0:d}", "forty-two");
// fmt::FormatError, description == "unknown format code 'd' for string"

// An object of any user-defined type for which there is an overloaded std::ostream insertion operator (operator<<) can be formatted
class Date {
    int year_, month_, day_;
    Date(int year, int month, int day) : year_(year), month_(month), day_(day) {}

    friend std::ostream &operator<<(std::ostream &os, const Date &d) {
        return os << d.year_ << '-' << d.month_ << '-' << d.day_;

std::string s = fmt::format("The date is {}", Date(2012, 12, 9));
// s == "The date is 2012-12-9"

// C++ Format can be used as a safe portable replacement for itoa:
fmt::MemoryWriter w;
w << 42;           // replaces itoa(42, buffer, 10)
w << fmt::hex(42); // replaces itoa(42, buffer, 16)

The fmt::format macros have been aliased in the Cinder::Format namespace to help avoid potential issues caused by using the fmt namespace which defines its own Color type. See the C++ Format documentation and particularly the format string syntax for more detail on usage.


Use of the Boost library is being deprecated within Cinder, CinderBlock authors are encouraged to not rely on it and Boost Format is quite a bit slower at compile and run time - see the C++ Format README for more benchmark details.


You can’t perform that action at this time.