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Update README.rst

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Victor Zverovich 2018-09-14 07:52:30 -07:00 committed by GitHub
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@ -108,24 +108,29 @@ Format strings can be checked at compile time:
format_to(buf, "{:x}", 42); // replaces itoa(42, buffer, 16)
// access the string using to_string(buf) or buf.data()
An object of any user-defined type for which there is an overloaded
:code:`std::ostream` insertion operator (``operator<<``) can be formatted:
Formatting of user-defined types is supported via a simple
`extension API <http://fmtlib.net/latest/api.html#formatting-user-defined-types>`_:
.. code:: c++
#include "fmt/ostream.h"
#include "fmt/format.h"
class Date {
int year_, month_, day_;
public:
Date(int year, int month, int day) : year_(year), month_(month), day_(day) {}
struct date {
int year, month, day;
};
friend std::ostream &operator<<(std::ostream &os, const Date &d) {
return os << d.year_ << '-' << d.month_ << '-' << d.day_;
template <>
struct fmt::formatter<date> {
template <typename ParseContext>
constexpr auto parse(ParseContext &ctx) { return ctx.begin(); }
template <typename FormatContext>
auto format(const date &d, FormatContext &ctx) {
return format_to(ctx.begin(), "{}-{}-{}", d.year, d.month, d.day);
}
};
std::string s = fmt::format("The date is {}", Date(2012, 12, 9));
std::string s = fmt::format("The date is {}", date{2012, 12, 9});
// s == "The date is 2012-12-9"
You can create your own functions similar to `format