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Update README.rst

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Victor Zverovich 2020-07-05 06:41:51 -07:00 committed by GitHub
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@ -78,6 +78,13 @@ Print ``Hello, world!`` to ``stdout``:
fmt::print("Hello, world!\n");
}
Format a string:
.. code:: c++
std::string s = fmt::format("The answer is {}.", 42);
// s == "The answer is 42."
Format a string using positional arguments:
.. code:: c++
@ -85,27 +92,29 @@ Format a string using positional arguments:
std::string s = fmt::format("I'd rather be {1} than {0}.", "right", "happy");
// s == "I'd rather be happy than right."
Print a chrono duration:
.. code:: c++
#include <fmt/chrono.h>
int main() {
using namespace std::chrono_literals;
fmt::print("Elapsed time: {}", 42ms);
}
prints "Elapsed time: 42ms".
Check a format string at compile time:
.. code:: c++
// test.cc
#include <fmt/format.h>
std::string s = format(FMT_STRING("{2}"), 42);
std::string s = format(FMT_STRING("{:d}"), "hello");
.. code::
$ c++ -Iinclude -std=c++14 test.cc
...
test.cc:4:17: note: in instantiation of function template specialization 'fmt::v5::format<S, int>' requested here
std::string s = format(FMT_STRING("{2}"), 42);
^
include/fmt/core.h:778:19: note: non-constexpr function 'on_error' cannot be used in a constant expression
ErrorHandler::on_error(message);
^
include/fmt/format.h:2226:16: note: in call to '&checker.context_->on_error(&"argument index out of range"[0])'
context_.on_error("argument index out of range");
^
gives a compile-time error because ``d`` is an invalid format specifier for a
string.
Use {fmt} as a safe portable replacement for ``itoa``
(`godbolt <https://godbolt.org/g/NXmpU4>`_):