mirror of
https://github.com/VCMP-SqMod/SqMod.git
synced 2026-08-15 12:17:11 +02:00
Use default cpp fmt build script.
This commit is contained in:
+544
@@ -0,0 +1,544 @@
|
||||
.. _string-formatting-api:
|
||||
|
||||
*************
|
||||
API Reference
|
||||
*************
|
||||
|
||||
The {fmt} library API consists of the following parts:
|
||||
|
||||
* :ref:`fmt/core.h <core-api>`: the core API providing main formatting functions
|
||||
for ``char``/UTF-8 with compile-time checks and minimal dependencies
|
||||
* :ref:`fmt/format.h <format-api>`: the full format API providing additional
|
||||
formatting functions and locale support
|
||||
* :ref:`fmt/ranges.h <ranges-api>`: formatting of ranges and tuples
|
||||
* :ref:`fmt/chrono.h <chrono-api>`: date and time formatting
|
||||
* :ref:`fmt/compile.h <compile-api>`: format string compilation
|
||||
* :ref:`fmt/color.h <color-api>`: terminal color and text style
|
||||
* :ref:`fmt/os.h <os-api>`: system APIs
|
||||
* :ref:`fmt/ostream.h <ostream-api>`: ``std::ostream`` support
|
||||
* :ref:`fmt/printf.h <printf-api>`: ``printf`` formatting
|
||||
* :ref:`fmt/xchar.h <xchar-api>`: optional ``wchar_t`` support
|
||||
|
||||
All functions and types provided by the library reside in namespace ``fmt`` and
|
||||
macros have prefix ``FMT_``.
|
||||
|
||||
.. _core-api:
|
||||
|
||||
Core API
|
||||
========
|
||||
|
||||
``fmt/core.h`` defines the core API which provides main formatting functions for
|
||||
``char``/UTF-8 with compile-time checks. It has minimal include dependencies for
|
||||
better compile times. This header is only beneficial when using {fmt} as a
|
||||
library and not in the header-only mode.
|
||||
|
||||
The following functions use :ref:`format string syntax <syntax>`
|
||||
similar to that of Python's `str.format
|
||||
<https://docs.python.org/3/library/stdtypes.html#str.format>`_.
|
||||
They take *fmt* and *args* as arguments.
|
||||
|
||||
*fmt* is a format string that contains literal text and replacement
|
||||
fields surrounded by braces ``{}``. The fields are replaced with formatted
|
||||
arguments in the resulting string. A function taking *fmt* doesn't
|
||||
participate in an overload resolution if the latter is not a string.
|
||||
|
||||
*args* is an argument list representing objects to be formatted.
|
||||
|
||||
.. _format:
|
||||
|
||||
.. doxygenfunction:: format(format_string<T...> fmt, T&&... args) -> std::string
|
||||
.. doxygenfunction:: vformat(string_view fmt, format_args args) -> std::string
|
||||
|
||||
.. doxygenfunction:: format_to(OutputIt out, format_string<T...> fmt, T&&... args) -> OutputIt
|
||||
.. doxygenfunction:: format_to_n(OutputIt out, size_t n, format_string<T...> fmt, const T&... args) -> format_to_n_result<OutputIt>
|
||||
.. doxygenfunction:: formatted_size(format_string<T...> fmt, T&&... args) -> size_t
|
||||
|
||||
.. doxygenstruct:: fmt::format_to_n_result
|
||||
:members:
|
||||
|
||||
.. _print:
|
||||
|
||||
.. doxygenfunction:: fmt::print(format_string<T...> fmt, T&&... args)
|
||||
.. doxygenfunction:: vprint(string_view fmt, format_args args)
|
||||
|
||||
.. doxygenfunction:: print(std::FILE *f, format_string<T...> fmt, T&&... args)
|
||||
.. doxygenfunction:: vprint(std::FILE *f, string_view fmt, format_args args)
|
||||
|
||||
Compile-time Format String Checks
|
||||
---------------------------------
|
||||
|
||||
Compile-time checks are enabled when using ``FMT_STRING``. They support built-in
|
||||
and string types as well as user-defined types with ``constexpr`` ``parse``
|
||||
functions in their ``formatter`` specializations.
|
||||
|
||||
.. doxygendefine:: FMT_STRING
|
||||
|
||||
To force the use of compile-time checks, define the preprocessor variable
|
||||
``FMT_ENFORCE_COMPILE_STRING``. When set, functions accepting ``FMT_STRING``
|
||||
will fail to compile with regular strings. Runtime-checked
|
||||
formatting is still possible using ``fmt::vformat``, ``fmt::vprint``, etc.
|
||||
|
||||
Named Arguments
|
||||
---------------
|
||||
|
||||
.. doxygenfunction:: fmt::arg(const S&, const T&)
|
||||
|
||||
Named arguments are not supported in compile-time checks at the moment.
|
||||
|
||||
Argument Lists
|
||||
--------------
|
||||
|
||||
You can create your own formatting function with compile-time checks and small
|
||||
binary footprint, for example (https://godbolt.org/z/oba4Mc):
|
||||
|
||||
.. code:: c++
|
||||
|
||||
#include <fmt/format.h>
|
||||
|
||||
void vlog(const char* file, int line, fmt::string_view format,
|
||||
fmt::format_args args) {
|
||||
fmt::print("{}: {}: ", file, line);
|
||||
fmt::vprint(format, args);
|
||||
}
|
||||
|
||||
template <typename S, typename... Args>
|
||||
void log(const char* file, int line, const S& format, Args&&... args) {
|
||||
vlog(file, line, format,
|
||||
fmt::make_args_checked<Args...>(format, args...));
|
||||
}
|
||||
|
||||
#define MY_LOG(format, ...) \
|
||||
log(__FILE__, __LINE__, FMT_STRING(format), __VA_ARGS__)
|
||||
|
||||
MY_LOG("invalid squishiness: {}", 42);
|
||||
|
||||
Note that ``vlog`` is not parameterized on argument types which improves compile
|
||||
times and reduces binary code size compared to a fully parameterized version.
|
||||
|
||||
.. doxygenfunction:: fmt::make_args_checked(const S&, const remove_reference_t<Args>&...)
|
||||
|
||||
.. doxygenfunction:: fmt::make_format_args(const Args&...)
|
||||
|
||||
.. doxygenclass:: fmt::format_arg_store
|
||||
:members:
|
||||
|
||||
.. doxygenclass:: fmt::dynamic_format_arg_store
|
||||
:members:
|
||||
|
||||
.. doxygenclass:: fmt::basic_format_args
|
||||
:members:
|
||||
|
||||
.. doxygentypedef:: fmt::format_args
|
||||
|
||||
.. doxygenclass:: fmt::basic_format_arg
|
||||
:members:
|
||||
|
||||
.. doxygenclass:: fmt::basic_format_context
|
||||
:members:
|
||||
|
||||
.. doxygentypedef:: fmt::format_context
|
||||
|
||||
Compatibility
|
||||
-------------
|
||||
|
||||
.. doxygenclass:: fmt::basic_string_view
|
||||
:members:
|
||||
|
||||
.. doxygentypedef:: fmt::string_view
|
||||
|
||||
Locale
|
||||
------
|
||||
|
||||
All formatting is locale-independent by default. Use the ``'L'`` format
|
||||
specifier to insert the appropriate number separator characters from the
|
||||
locale::
|
||||
|
||||
#include <fmt/core.h>
|
||||
#include <locale>
|
||||
|
||||
std::locale::global(std::locale("en_US.UTF-8"));
|
||||
auto s = fmt::format("{:L}", 1000000); // s == "1,000,000"
|
||||
|
||||
.. _format-api:
|
||||
|
||||
Format API
|
||||
==========
|
||||
|
||||
``fmt/format.h`` defines the full format API providing additional formatting
|
||||
functions and locale support.
|
||||
|
||||
.. _udt:
|
||||
|
||||
Formatting User-defined Types
|
||||
-----------------------------
|
||||
|
||||
To make a user-defined type formattable, specialize the ``formatter<T>`` struct
|
||||
template and implement ``parse`` and ``format`` methods::
|
||||
|
||||
#include <fmt/format.h>
|
||||
|
||||
struct point { double x, y; };
|
||||
|
||||
template <> struct fmt::formatter<point> {
|
||||
// Presentation format: 'f' - fixed, 'e' - exponential.
|
||||
char presentation = 'f';
|
||||
|
||||
// Parses format specifications of the form ['f' | 'e'].
|
||||
constexpr auto parse(format_parse_context& ctx) -> decltype(ctx.begin()) {
|
||||
// [ctx.begin(), ctx.end()) is a character range that contains a part of
|
||||
// the format string starting from the format specifications to be parsed,
|
||||
// e.g. in
|
||||
//
|
||||
// fmt::format("{:f} - point of interest", point{1, 2});
|
||||
//
|
||||
// the range will contain "f} - point of interest". The formatter should
|
||||
// parse specifiers until '}' or the end of the range. In this example
|
||||
// the formatter should parse the 'f' specifier and return an iterator
|
||||
// pointing to '}'.
|
||||
|
||||
// Parse the presentation format and store it in the formatter:
|
||||
auto it = ctx.begin(), end = ctx.end();
|
||||
if (it != end && (*it == 'f' || *it == 'e')) presentation = *it++;
|
||||
|
||||
// Check if reached the end of the range:
|
||||
if (it != end && *it != '}')
|
||||
throw format_error("invalid format");
|
||||
|
||||
// Return an iterator past the end of the parsed range:
|
||||
return it;
|
||||
}
|
||||
|
||||
// Formats the point p using the parsed format specification (presentation)
|
||||
// stored in this formatter.
|
||||
template <typename FormatContext>
|
||||
auto format(const point& p, FormatContext& ctx) -> decltype(ctx.out()) {
|
||||
// ctx.out() is an output iterator to write to.
|
||||
return format_to(
|
||||
ctx.out(),
|
||||
presentation == 'f' ? "({:.1f}, {:.1f})" : "({:.1e}, {:.1e})",
|
||||
p.x, p.y);
|
||||
}
|
||||
};
|
||||
|
||||
Then you can pass objects of type ``point`` to any formatting function::
|
||||
|
||||
point p = {1, 2};
|
||||
std::string s = fmt::format("{:f}", p);
|
||||
// s == "(1.0, 2.0)"
|
||||
|
||||
You can also reuse existing formatters via inheritance or composition, for
|
||||
example::
|
||||
|
||||
enum class color {red, green, blue};
|
||||
|
||||
template <> struct fmt::formatter<color>: formatter<string_view> {
|
||||
// parse is inherited from formatter<string_view>.
|
||||
template <typename FormatContext>
|
||||
auto format(color c, FormatContext& ctx) {
|
||||
string_view name = "unknown";
|
||||
switch (c) {
|
||||
case color::red: name = "red"; break;
|
||||
case color::green: name = "green"; break;
|
||||
case color::blue: name = "blue"; break;
|
||||
}
|
||||
return formatter<string_view>::format(name, ctx);
|
||||
}
|
||||
};
|
||||
|
||||
Since ``parse`` is inherited from ``formatter<string_view>`` it will recognize
|
||||
all string format specifications, for example
|
||||
|
||||
.. code-block:: c++
|
||||
|
||||
fmt::format("{:>10}", color::blue)
|
||||
|
||||
will return ``" blue"``.
|
||||
|
||||
You can also write a formatter for a hierarchy of classes::
|
||||
|
||||
#include <type_traits>
|
||||
#include <fmt/format.h>
|
||||
|
||||
struct A {
|
||||
virtual ~A() {}
|
||||
virtual std::string name() const { return "A"; }
|
||||
};
|
||||
|
||||
struct B : A {
|
||||
virtual std::string name() const { return "B"; }
|
||||
};
|
||||
|
||||
template <typename T>
|
||||
struct fmt::formatter<T, std::enable_if_t<std::is_base_of<A, T>::value, char>> :
|
||||
fmt::formatter<std::string> {
|
||||
template <typename FormatCtx>
|
||||
auto format(const A& a, FormatCtx& ctx) {
|
||||
return fmt::formatter<std::string>::format(a.name(), ctx);
|
||||
}
|
||||
};
|
||||
|
||||
int main() {
|
||||
B b;
|
||||
A& a = b;
|
||||
fmt::print("{}", a); // prints "B"
|
||||
}
|
||||
|
||||
If a type provides both a ``formatter`` specialization and an implicit
|
||||
conversion to a formattable type, the specialization takes precedence over the
|
||||
conversion.
|
||||
|
||||
.. doxygenclass:: fmt::basic_format_parse_context
|
||||
:members:
|
||||
|
||||
Literal-based API
|
||||
-----------------
|
||||
|
||||
The following user-defined literals are defined in ``fmt/format.h``.
|
||||
|
||||
.. doxygenfunction:: operator""_format(const char *s, size_t n) -> detail::udl_formatter<char>
|
||||
|
||||
.. doxygenfunction:: operator""_a(const char *s, size_t) -> detail::udl_arg<char>
|
||||
|
||||
Utilities
|
||||
---------
|
||||
|
||||
.. doxygenfunction:: fmt::ptr(T p) -> const void*
|
||||
.. doxygenfunction:: fmt::ptr(const std::unique_ptr<T> &p) -> const void*
|
||||
.. doxygenfunction:: fmt::ptr(const std::shared_ptr<T> &p) -> const void*
|
||||
|
||||
.. doxygenfunction:: fmt::to_string(const T &value) -> std::string
|
||||
|
||||
.. doxygenfunction:: fmt::to_string_view(const Char *s) -> basic_string_view<Char>
|
||||
|
||||
.. doxygenfunction:: fmt::join(Range &&range, string_view sep) -> join_view<detail::iterator_t<Range>, detail::sentinel_t<Range>>
|
||||
|
||||
.. doxygenfunction:: fmt::join(It begin, Sentinel end, string_view sep) -> join_view<It, Sentinel>
|
||||
|
||||
.. doxygenclass:: fmt::detail::buffer
|
||||
:members:
|
||||
|
||||
.. doxygenclass:: fmt::basic_memory_buffer
|
||||
:protected-members:
|
||||
:members:
|
||||
|
||||
System Errors
|
||||
-------------
|
||||
|
||||
{fmt} does not use ``errno`` to communicate errors to the user, but it may call
|
||||
system functions which set ``errno``. Users should not make any assumptions
|
||||
about the value of ``errno`` being preserved by library functions.
|
||||
|
||||
.. doxygenfunction:: fmt::system_error
|
||||
|
||||
.. doxygenfunction:: fmt::format_system_error
|
||||
|
||||
Custom Allocators
|
||||
-----------------
|
||||
|
||||
The {fmt} library supports custom dynamic memory allocators.
|
||||
A custom allocator class can be specified as a template argument to
|
||||
:class:`fmt::basic_memory_buffer`::
|
||||
|
||||
using custom_memory_buffer =
|
||||
fmt::basic_memory_buffer<char, fmt::inline_buffer_size, custom_allocator>;
|
||||
|
||||
It is also possible to write a formatting function that uses a custom
|
||||
allocator::
|
||||
|
||||
using custom_string =
|
||||
std::basic_string<char, std::char_traits<char>, custom_allocator>;
|
||||
|
||||
custom_string vformat(custom_allocator alloc, fmt::string_view format_str,
|
||||
fmt::format_args args) {
|
||||
custom_memory_buffer buf(alloc);
|
||||
fmt::vformat_to(buf, format_str, args);
|
||||
return custom_string(buf.data(), buf.size(), alloc);
|
||||
}
|
||||
|
||||
template <typename ...Args>
|
||||
inline custom_string format(custom_allocator alloc,
|
||||
fmt::string_view format_str,
|
||||
const Args& ... args) {
|
||||
return vformat(alloc, format_str, fmt::make_format_args(args...));
|
||||
}
|
||||
|
||||
The allocator will be used for the output container only. Formatting functions
|
||||
normally don't do any allocations for built-in and string types except for
|
||||
non-default floating-point formatting that occasionally falls back on
|
||||
``sprintf``.
|
||||
|
||||
.. _ranges-api:
|
||||
|
||||
Ranges and Tuple Formatting
|
||||
===========================
|
||||
|
||||
The library also supports convenient formatting of ranges and tuples::
|
||||
|
||||
#include <fmt/ranges.h>
|
||||
|
||||
std::tuple<char, int, float> t{'a', 1, 2.0f};
|
||||
// Prints "('a', 1, 2.0)"
|
||||
fmt::print("{}", t);
|
||||
|
||||
|
||||
NOTE: currently, the overload of ``fmt::join`` for iterables exists in the main
|
||||
``format.h`` header, but expect this to change in the future.
|
||||
|
||||
Using ``fmt::join``, you can separate tuple elements with a custom separator::
|
||||
|
||||
#include <fmt/ranges.h>
|
||||
|
||||
std::tuple<int, char> t = {1, 'a'};
|
||||
// Prints "1, a"
|
||||
fmt::print("{}", fmt::join(t, ", "));
|
||||
|
||||
.. _chrono-api:
|
||||
|
||||
Date and Time Formatting
|
||||
========================
|
||||
|
||||
``fmt/chrono.h`` provides formatters for
|
||||
|
||||
* `std::chrono::duration <https://en.cppreference.com/w/cpp/chrono/duration>`_
|
||||
* `std::chrono::time_point
|
||||
<https://en.cppreference.com/w/cpp/chrono/time_point>`_
|
||||
* `std::tm <https://en.cppreference.com/w/cpp/chrono/c/tm>`_
|
||||
|
||||
The format syntax is described in :ref:`chrono-specs`.
|
||||
|
||||
**Example**::
|
||||
|
||||
#include <fmt/chrono.h>
|
||||
|
||||
int main() {
|
||||
std::time_t t = std::time(nullptr);
|
||||
|
||||
// Prints "The date is 2020-11-07." (with the current date):
|
||||
fmt::print("The date is {:%Y-%m-%d}.", fmt::localtime(t));
|
||||
|
||||
using namespace std::literals::chrono_literals;
|
||||
|
||||
// Prints "Default format: 42s 100ms":
|
||||
fmt::print("Default format: {} {}\n", 42s, 100ms);
|
||||
|
||||
// Prints "strftime-like format: 03:15:30":
|
||||
fmt::print("strftime-like format: {:%H:%M:%S}\n", 3h + 15min + 30s);
|
||||
}
|
||||
|
||||
.. doxygenfunction:: localtime(std::time_t time)
|
||||
|
||||
.. doxygenfunction:: gmtime(std::time_t time)
|
||||
|
||||
.. _compile-api:
|
||||
|
||||
Format string compilation
|
||||
=========================
|
||||
|
||||
``fmt/compile.h`` provides format string compilation support when using
|
||||
``FMT_COMPILE``. Format strings are parsed, checked and converted into efficient
|
||||
formatting code at compile-time. This supports arguments of built-in and string
|
||||
types as well as user-defined types with ``constexpr`` ``parse`` functions in
|
||||
their ``formatter`` specializations. Format string compilation can generate more
|
||||
binary code compared to the default API and is only recommended in places where
|
||||
formatting is a performance bottleneck.
|
||||
|
||||
.. doxygendefine:: FMT_COMPILE
|
||||
|
||||
.. _color-api:
|
||||
|
||||
Terminal color and text style
|
||||
=============================
|
||||
|
||||
``fmt/color.h`` provides support for terminal color and text style output.
|
||||
|
||||
.. doxygenfunction:: print(const text_style &ts, const S &format_str, const Args&... args)
|
||||
|
||||
.. doxygenfunction:: fg(detail::color_type)
|
||||
|
||||
.. doxygenfunction:: bg(detail::color_type)
|
||||
|
||||
.. _os-api:
|
||||
|
||||
System APIs
|
||||
===========
|
||||
|
||||
.. doxygenclass:: fmt::ostream
|
||||
:members:
|
||||
|
||||
.. doxygenfunction:: fmt::windows_error
|
||||
:members:
|
||||
|
||||
.. _ostream-api:
|
||||
|
||||
``std::ostream`` Support
|
||||
========================
|
||||
|
||||
``fmt/ostream.h`` provides ``std::ostream`` support including formatting of
|
||||
user-defined types that have an overloaded insertion operator (``operator<<``)::
|
||||
|
||||
#include <fmt/ostream.h>
|
||||
|
||||
class date {
|
||||
int year_, month_, day_;
|
||||
public:
|
||||
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"
|
||||
|
||||
{fmt} only supports insertion operators that are defined in the same namespaces
|
||||
as the types they format and can be found with the argument-dependent lookup.
|
||||
|
||||
.. doxygenfunction:: print(std::basic_ostream<Char> &os, const S &format_str, Args&&... args)
|
||||
|
||||
.. _printf-api:
|
||||
|
||||
``printf`` Formatting
|
||||
=====================
|
||||
|
||||
The header ``fmt/printf.h`` provides ``printf``-like formatting functionality.
|
||||
The following functions use `printf format string syntax
|
||||
<https://pubs.opengroup.org/onlinepubs/009695399/functions/fprintf.html>`_ with
|
||||
the POSIX extension for positional arguments. Unlike their standard
|
||||
counterparts, the ``fmt`` functions are type-safe and throw an exception if an
|
||||
argument type doesn't match its format specification.
|
||||
|
||||
.. doxygenfunction:: printf(const S &format_str, const T&... args)
|
||||
|
||||
.. doxygenfunction:: fprintf(std::FILE *f, const S &fmt, const T&... args) -> int
|
||||
|
||||
.. doxygenfunction:: sprintf(const S&, const T&...)
|
||||
|
||||
.. _xchar-api:
|
||||
|
||||
``wchar_t`` Support
|
||||
===================
|
||||
|
||||
The optional header ``fmt/wchar_t.h`` provides support for ``wchar_t`` and
|
||||
exotic character types.
|
||||
|
||||
.. doxygenstruct:: fmt::is_char
|
||||
|
||||
.. doxygentypedef:: fmt::wstring_view
|
||||
|
||||
.. doxygentypedef:: fmt::wformat_context
|
||||
|
||||
.. doxygenfunction:: fmt::to_wstring(const T &value)
|
||||
|
||||
Compatibility with C++20 ``std::format``
|
||||
========================================
|
||||
|
||||
{fmt} implements nearly all of the `C++20 formatting library
|
||||
<https://en.cppreference.com/w/cpp/utility/format>`_ with the following
|
||||
differences:
|
||||
|
||||
* Names are defined in the ``fmt`` namespace instead of ``std`` to avoid
|
||||
collisions with standard library implementations.
|
||||
* Width calculation doesn't use grapheme clusterization. The latter has been
|
||||
implemented in a separate branch but hasn't been integrated yet.
|
||||
* Most C++20 chrono types are not supported yet.
|
||||
+10
@@ -0,0 +1,10 @@
|
||||
########
|
||||
Contents
|
||||
########
|
||||
|
||||
.. toctree::
|
||||
:maxdepth: 2
|
||||
|
||||
usage
|
||||
api
|
||||
syntax
|
||||
+198
@@ -0,0 +1,198 @@
|
||||
Overview
|
||||
========
|
||||
|
||||
**{fmt}** is an open-source formatting library providing a fast and safe
|
||||
alternative to C stdio and C++ iostreams.
|
||||
|
||||
.. raw:: html
|
||||
|
||||
<div class="panel panel-default">
|
||||
<div class="panel-heading">What users say:</div>
|
||||
<div class="panel-body">
|
||||
Thanks for creating this library. It’s been a hole in C++ for
|
||||
a long time. I’ve used both <code>boost::format</code> and
|
||||
<code>loki::SPrintf</code>, and neither felt like the right answer.
|
||||
This does.
|
||||
</div>
|
||||
</div>
|
||||
|
||||
.. _format-api-intro:
|
||||
|
||||
Format API
|
||||
----------
|
||||
|
||||
The format API is similar in spirit to the C ``printf`` family of function but
|
||||
is safer, simpler and several times `faster
|
||||
<https://www.zverovich.net/2020/06/13/fast-int-to-string-revisited.html>`_
|
||||
than common standard library implementations.
|
||||
The `format string syntax <syntax.html>`_ is similar to the one used by
|
||||
`str.format <https://docs.python.org/3/library/stdtypes.html#str.format>`_ in
|
||||
Python:
|
||||
|
||||
.. code:: c++
|
||||
|
||||
std::string s = fmt::format("The answer is {}.", 42);
|
||||
|
||||
The ``fmt::format`` function returns a string "The answer is 42.". You can use
|
||||
``fmt::memory_buffer`` to avoid constructing ``std::string``:
|
||||
|
||||
.. code:: c++
|
||||
|
||||
auto out = fmt::memory_buffer();
|
||||
format_to(std::back_inserter(out),
|
||||
"For a moment, {} happened.", "nothing");
|
||||
auto data = out.data(); // pointer to the formatted data
|
||||
auto size = out.size(); // size of the formatted data
|
||||
|
||||
The ``fmt::print`` function performs formatting and writes the result to a stream:
|
||||
|
||||
.. code:: c++
|
||||
|
||||
fmt::print(stderr, "System error code = {}\n", errno);
|
||||
|
||||
If you omit the file argument the function will print to ``stdout``:
|
||||
|
||||
.. code:: c++
|
||||
|
||||
fmt::print("Don't {}\n", "panic");
|
||||
|
||||
The format API also supports positional arguments useful for localization:
|
||||
|
||||
.. code:: c++
|
||||
|
||||
fmt::print("I'd rather be {1} than {0}.", "right", "happy");
|
||||
|
||||
You can pass named arguments with ``fmt::arg``:
|
||||
|
||||
.. code:: c++
|
||||
|
||||
fmt::print("Hello, {name}! The answer is {number}. Goodbye, {name}.",
|
||||
fmt::arg("name", "World"), fmt::arg("number", 42));
|
||||
|
||||
If your compiler supports C++11 user-defined literals, the suffix ``_a`` offers
|
||||
an alternative, slightly terser syntax for named arguments:
|
||||
|
||||
.. code:: c++
|
||||
|
||||
using namespace fmt::literals;
|
||||
fmt::print("Hello, {name}! The answer is {number}. Goodbye, {name}.",
|
||||
"name"_a="World", "number"_a=42);
|
||||
|
||||
.. _safety:
|
||||
|
||||
Safety
|
||||
------
|
||||
|
||||
The library is fully type safe, automatic memory management prevents buffer
|
||||
overflow, errors in format strings are reported using exceptions or at compile
|
||||
time. For example, the code
|
||||
|
||||
.. code:: c++
|
||||
|
||||
fmt::format("The answer is {:d}", "forty-two");
|
||||
|
||||
throws the ``format_error`` exception because the argument ``"forty-two"`` is a
|
||||
string while the format code ``d`` only applies to integers.
|
||||
|
||||
The code
|
||||
|
||||
.. code:: c++
|
||||
|
||||
format(FMT_STRING("The answer is {:d}"), "forty-two");
|
||||
|
||||
reports a compile-time error on compilers that support relaxed ``constexpr``.
|
||||
See `here <api.html#c.fmt>`_ for details.
|
||||
|
||||
The following code
|
||||
|
||||
.. code:: c++
|
||||
|
||||
fmt::format("Cyrillic letter {}", L'\x42e');
|
||||
|
||||
produces a compile-time error because wide character ``L'\x42e'`` cannot be
|
||||
formatted into a narrow string. For comparison, writing a wide character to
|
||||
``std::ostream`` results in its numeric value being written to the stream
|
||||
(i.e. 1070 instead of letter 'ю' which is represented by ``L'\x42e'`` if we
|
||||
use Unicode) which is rarely desirable.
|
||||
|
||||
Compact Binary Code
|
||||
-------------------
|
||||
|
||||
The library produces compact per-call compiled code. For example
|
||||
(`godbolt <https://godbolt.org/g/TZU4KF>`_),
|
||||
|
||||
.. code:: c++
|
||||
|
||||
#include <fmt/core.h>
|
||||
|
||||
int main() {
|
||||
fmt::print("The answer is {}.", 42);
|
||||
}
|
||||
|
||||
compiles to just
|
||||
|
||||
.. code:: asm
|
||||
|
||||
main: # @main
|
||||
sub rsp, 24
|
||||
mov qword ptr [rsp], 42
|
||||
mov rcx, rsp
|
||||
mov edi, offset .L.str
|
||||
mov esi, 17
|
||||
mov edx, 1
|
||||
call fmt::v7::vprint(fmt::v7::basic_string_view<char>, fmt::v7::format_args)
|
||||
xor eax, eax
|
||||
add rsp, 24
|
||||
ret
|
||||
.L.str:
|
||||
.asciz "The answer is {}."
|
||||
|
||||
.. _portability:
|
||||
|
||||
Portability
|
||||
-----------
|
||||
|
||||
The library is highly portable and relies only on a small set of C++11 features:
|
||||
|
||||
* variadic templates
|
||||
* type traits
|
||||
* rvalue references
|
||||
* decltype
|
||||
* trailing return types
|
||||
* deleted functions
|
||||
* alias templates
|
||||
|
||||
These are available in GCC 4.8, Clang 3.4, MSVC 19.0 (2015) and more recent
|
||||
compiler version. For older compilers use {fmt} `version 4.x
|
||||
<https://github.com/fmtlib/fmt/releases/tag/4.1.0>`_ which is maintained and
|
||||
only requires C++98.
|
||||
|
||||
The output of all formatting functions is consistent across platforms.
|
||||
For example,
|
||||
|
||||
.. code::
|
||||
|
||||
fmt::print("{}", std::numeric_limits<double>::infinity());
|
||||
|
||||
always prints ``inf`` while the output of ``printf`` is platform-dependent.
|
||||
|
||||
.. _ease-of-use:
|
||||
|
||||
Ease of Use
|
||||
-----------
|
||||
|
||||
{fmt} has a small self-contained code base with the core library consisting of
|
||||
just three header files and no external dependencies.
|
||||
A permissive MIT `license <https://github.com/fmtlib/fmt#license>`_ allows
|
||||
using the library both in open-source and commercial projects.
|
||||
|
||||
`Learn more... <contents.html>`_
|
||||
|
||||
.. raw:: html
|
||||
|
||||
<a class="btn btn-success" href="https://github.com/fmtlib/fmt">GitHub Repository</a>
|
||||
|
||||
<div class="section footer">
|
||||
<iframe src="https://ghbtns.com/github-btn.html?user=fmtlib&repo=fmt&type=watch&count=true"
|
||||
class="github-btn" width="100" height="20"></iframe>
|
||||
</div>
|
||||
+486
@@ -0,0 +1,486 @@
|
||||
.. _syntax:
|
||||
|
||||
********************
|
||||
Format String Syntax
|
||||
********************
|
||||
|
||||
Formatting functions such as :ref:`fmt::format() <format>` and
|
||||
:ref:`fmt::print() <print>` use the same format string syntax described in this
|
||||
section.
|
||||
|
||||
Format strings contain "replacement fields" surrounded by curly braces ``{}``.
|
||||
Anything that is not contained in braces is considered literal text, which is
|
||||
copied unchanged to the output. If you need to include a brace character in the
|
||||
literal text, it can be escaped by doubling: ``{{`` and ``}}``.
|
||||
|
||||
The grammar for a replacement field is as follows:
|
||||
|
||||
.. productionlist:: sf
|
||||
replacement_field: "{" [`arg_id`] [":" (`format_spec` | `chrono_format_spec`)] "}"
|
||||
arg_id: `integer` | `identifier`
|
||||
integer: `digit`+
|
||||
digit: "0"..."9"
|
||||
identifier: `id_start` `id_continue`*
|
||||
id_start: "a"..."z" | "A"..."Z" | "_"
|
||||
id_continue: `id_start` | `digit`
|
||||
|
||||
In less formal terms, the replacement field can start with an *arg_id*
|
||||
that specifies the argument whose value is to be formatted and inserted into
|
||||
the output instead of the replacement field.
|
||||
The *arg_id* is optionally followed by a *format_spec*, which is preceded by a
|
||||
colon ``':'``. These specify a non-default format for the replacement value.
|
||||
|
||||
See also the :ref:`formatspec` section.
|
||||
|
||||
If the numerical arg_ids in a format string are 0, 1, 2, ... in sequence,
|
||||
they can all be omitted (not just some) and the numbers 0, 1, 2, ... will be
|
||||
automatically inserted in that order.
|
||||
|
||||
Named arguments can be referred to by their names or indices.
|
||||
|
||||
Some simple format string examples::
|
||||
|
||||
"First, thou shalt count to {0}" // References the first argument
|
||||
"Bring me a {}" // Implicitly references the first argument
|
||||
"From {} to {}" // Same as "From {0} to {1}"
|
||||
|
||||
The *format_spec* field contains a specification of how the value should be
|
||||
presented, including such details as field width, alignment, padding, decimal
|
||||
precision and so on. Each value type can define its own "formatting
|
||||
mini-language" or interpretation of the *format_spec*.
|
||||
|
||||
Most built-in types support a common formatting mini-language, which is
|
||||
described in the next section.
|
||||
|
||||
A *format_spec* field can also include nested replacement fields in certain
|
||||
positions within it. These nested replacement fields can contain only an
|
||||
argument id; format specifications are not allowed. This allows the formatting
|
||||
of a value to be dynamically specified.
|
||||
|
||||
See the :ref:`formatexamples` section for some examples.
|
||||
|
||||
.. _formatspec:
|
||||
|
||||
Format Specification Mini-Language
|
||||
==================================
|
||||
|
||||
"Format specifications" are used within replacement fields contained within a
|
||||
format string to define how individual values are presented (see
|
||||
:ref:`syntax`). Each formattable type may define how the format
|
||||
specification is to be interpreted.
|
||||
|
||||
Most built-in types implement the following options for format specifications,
|
||||
although some of the formatting options are only supported by the numeric types.
|
||||
|
||||
The general form of a *standard format specifier* is:
|
||||
|
||||
.. productionlist:: sf
|
||||
format_spec: [[`fill`]`align`][`sign`]["#"]["0"][`width`]["." `precision`]["L"][`type`]
|
||||
fill: <a character other than '{' or '}'>
|
||||
align: "<" | ">" | "^"
|
||||
sign: "+" | "-" | " "
|
||||
width: `integer` | "{" [`arg_id`] "}"
|
||||
precision: `integer` | "{" [`arg_id`] "}"
|
||||
type: "a" | "A" | "b" | "B" | "c" | "d" | "e" | "E" | "f" | "F" | "g" | "G" |
|
||||
: "o" | "p" | "s" | "x" | "X"
|
||||
|
||||
The *fill* character can be any Unicode code point other than ``'{'`` or
|
||||
``'}'``. The presence of a fill character is signaled by the character following
|
||||
it, which must be one of the alignment options. If the second character of
|
||||
*format_spec* is not a valid alignment option, then it is assumed that both the
|
||||
fill character and the alignment option are absent.
|
||||
|
||||
The meaning of the various alignment options is as follows:
|
||||
|
||||
+---------+----------------------------------------------------------+
|
||||
| Option | Meaning |
|
||||
+=========+==========================================================+
|
||||
| ``'<'`` | Forces the field to be left-aligned within the available |
|
||||
| | space (this is the default for most objects). |
|
||||
+---------+----------------------------------------------------------+
|
||||
| ``'>'`` | Forces the field to be right-aligned within the |
|
||||
| | available space (this is the default for numbers). |
|
||||
+---------+----------------------------------------------------------+
|
||||
| ``'^'`` | Forces the field to be centered within the available |
|
||||
| | space. |
|
||||
+---------+----------------------------------------------------------+
|
||||
|
||||
Note that unless a minimum field width is defined, the field width will always
|
||||
be the same size as the data to fill it, so that the alignment option has no
|
||||
meaning in this case.
|
||||
|
||||
The *sign* option is only valid for number types, and can be one of the
|
||||
following:
|
||||
|
||||
+---------+----------------------------------------------------------+
|
||||
| Option | Meaning |
|
||||
+=========+==========================================================+
|
||||
| ``'+'`` | indicates that a sign should be used for both |
|
||||
| | positive as well as negative numbers. |
|
||||
+---------+----------------------------------------------------------+
|
||||
| ``'-'`` | indicates that a sign should be used only for negative |
|
||||
| | numbers (this is the default behavior). |
|
||||
+---------+----------------------------------------------------------+
|
||||
| space | indicates that a leading space should be used on |
|
||||
| | positive numbers, and a minus sign on negative numbers. |
|
||||
+---------+----------------------------------------------------------+
|
||||
|
||||
The ``'#'`` option causes the "alternate form" to be used for the
|
||||
conversion. The alternate form is defined differently for different
|
||||
types. This option is only valid for integer and floating-point types.
|
||||
For integers, when binary, octal, or hexadecimal output is used, this
|
||||
option adds the prefix respective ``"0b"`` (``"0B"``), ``"0"``, or
|
||||
``"0x"`` (``"0X"``) to the output value. Whether the prefix is
|
||||
lower-case or upper-case is determined by the case of the type
|
||||
specifier, for example, the prefix ``"0x"`` is used for the type ``'x'``
|
||||
and ``"0X"`` is used for ``'X'``. For floating-point numbers the
|
||||
alternate form causes the result of the conversion to always contain a
|
||||
decimal-point character, even if no digits follow it. Normally, a
|
||||
decimal-point character appears in the result of these conversions
|
||||
only if a digit follows it. In addition, for ``'g'`` and ``'G'``
|
||||
conversions, trailing zeros are not removed from the result.
|
||||
|
||||
.. ifconfig:: False
|
||||
|
||||
The ``','`` option signals the use of a comma for a thousands separator.
|
||||
For a locale aware separator, use the ``'L'`` integer presentation type
|
||||
instead.
|
||||
|
||||
*width* is a decimal integer defining the minimum field width. If not
|
||||
specified, then the field width will be determined by the content.
|
||||
|
||||
Preceding the *width* field by a zero (``'0'``) character enables sign-aware
|
||||
zero-padding for numeric types. It forces the padding to be placed after the
|
||||
sign or base (if any) but before the digits. This is used for printing fields in
|
||||
the form '+000000120'. This option is only valid for numeric types and it has no
|
||||
effect on formatting of infinity and NaN.
|
||||
|
||||
The *precision* is a decimal number indicating how many digits should be
|
||||
displayed after the decimal point for a floating-point value formatted with
|
||||
``'f'`` and ``'F'``, or before and after the decimal point for a floating-point
|
||||
value formatted with ``'g'`` or ``'G'``. For non-number types the field
|
||||
indicates the maximum field size - in other words, how many characters will be
|
||||
used from the field content. The *precision* is not allowed for integer,
|
||||
character, Boolean, and pointer values.
|
||||
|
||||
The ``'L'`` option uses the current locale setting to insert the appropriate
|
||||
number separator characters. This option is only valid for numeric types.
|
||||
|
||||
Finally, the *type* determines how the data should be presented.
|
||||
|
||||
The available string presentation types are:
|
||||
|
||||
+---------+----------------------------------------------------------+
|
||||
| Type | Meaning |
|
||||
+=========+==========================================================+
|
||||
| ``'s'`` | String format. This is the default type for strings and |
|
||||
| | may be omitted. |
|
||||
+---------+----------------------------------------------------------+
|
||||
| none | The same as ``'s'``. |
|
||||
+---------+----------------------------------------------------------+
|
||||
|
||||
The available character presentation types are:
|
||||
|
||||
+---------+----------------------------------------------------------+
|
||||
| Type | Meaning |
|
||||
+=========+==========================================================+
|
||||
| ``'c'`` | Character format. This is the default type for |
|
||||
| | characters and may be omitted. |
|
||||
+---------+----------------------------------------------------------+
|
||||
| none | The same as ``'c'``. |
|
||||
+---------+----------------------------------------------------------+
|
||||
|
||||
The available integer presentation types are:
|
||||
|
||||
+---------+----------------------------------------------------------+
|
||||
| Type | Meaning |
|
||||
+=========+==========================================================+
|
||||
| ``'b'`` | Binary format. Outputs the number in base 2. Using the |
|
||||
| | ``'#'`` option with this type adds the prefix ``"0b"`` |
|
||||
| | to the output value. |
|
||||
+---------+----------------------------------------------------------+
|
||||
| ``'B'`` | Binary format. Outputs the number in base 2. Using the |
|
||||
| | ``'#'`` option with this type adds the prefix ``"0B"`` |
|
||||
| | to the output value. |
|
||||
+---------+----------------------------------------------------------+
|
||||
| ``'c'`` | Character format. Outputs the number as a character. |
|
||||
+---------+----------------------------------------------------------+
|
||||
| ``'d'`` | Decimal integer. Outputs the number in base 10. |
|
||||
+---------+----------------------------------------------------------+
|
||||
| ``'o'`` | Octal format. Outputs the number in base 8. |
|
||||
+---------+----------------------------------------------------------+
|
||||
| ``'x'`` | Hex format. Outputs the number in base 16, using |
|
||||
| | lower-case letters for the digits above 9. Using the |
|
||||
| | ``'#'`` option with this type adds the prefix ``"0x"`` |
|
||||
| | to the output value. |
|
||||
+---------+----------------------------------------------------------+
|
||||
| ``'X'`` | Hex format. Outputs the number in base 16, using |
|
||||
| | upper-case letters for the digits above 9. Using the |
|
||||
| | ``'#'`` option with this type adds the prefix ``"0X"`` |
|
||||
| | to the output value. |
|
||||
+---------+----------------------------------------------------------+
|
||||
| none | The same as ``'d'``. |
|
||||
+---------+----------------------------------------------------------+
|
||||
|
||||
Integer presentation types can also be used with character and Boolean values.
|
||||
Boolean values are formatted using textual representation, either ``true`` or
|
||||
``false``, if the presentation type is not specified.
|
||||
|
||||
The available presentation types for floating-point values are:
|
||||
|
||||
+---------+----------------------------------------------------------+
|
||||
| Type | Meaning |
|
||||
+=========+==========================================================+
|
||||
| ``'a'`` | Hexadecimal floating point format. Prints the number in |
|
||||
| | base 16 with prefix ``"0x"`` and lower-case letters for |
|
||||
| | digits above 9. Uses ``'p'`` to indicate the exponent. |
|
||||
+---------+----------------------------------------------------------+
|
||||
| ``'A'`` | Same as ``'a'`` except it uses upper-case letters for |
|
||||
| | the prefix, digits above 9 and to indicate the exponent. |
|
||||
+---------+----------------------------------------------------------+
|
||||
| ``'e'`` | Exponent notation. Prints the number in scientific |
|
||||
| | notation using the letter 'e' to indicate the exponent. |
|
||||
+---------+----------------------------------------------------------+
|
||||
| ``'E'`` | Exponent notation. Same as ``'e'`` except it uses an |
|
||||
| | upper-case ``'E'`` as the separator character. |
|
||||
+---------+----------------------------------------------------------+
|
||||
| ``'f'`` | Fixed point. Displays the number as a fixed-point |
|
||||
| | number. |
|
||||
+---------+----------------------------------------------------------+
|
||||
| ``'F'`` | Fixed point. Same as ``'f'``, but converts ``nan`` to |
|
||||
| | ``NAN`` and ``inf`` to ``INF``. |
|
||||
+---------+----------------------------------------------------------+
|
||||
| ``'g'`` | General format. For a given precision ``p >= 1``, |
|
||||
| | this rounds the number to ``p`` significant digits and |
|
||||
| | then formats the result in either fixed-point format |
|
||||
| | or in scientific notation, depending on its magnitude. |
|
||||
| | |
|
||||
| | A precision of ``0`` is treated as equivalent to a |
|
||||
| | precision of ``1``. |
|
||||
+---------+----------------------------------------------------------+
|
||||
| ``'G'`` | General format. Same as ``'g'`` except switches to |
|
||||
| | ``'E'`` if the number gets too large. The |
|
||||
| | representations of infinity and NaN are uppercased, too. |
|
||||
+---------+----------------------------------------------------------+
|
||||
| none | Similar to ``'g'``, except that the default precision is |
|
||||
| | as high as needed to represent the particular value. |
|
||||
+---------+----------------------------------------------------------+
|
||||
|
||||
.. ifconfig:: False
|
||||
|
||||
+---------+----------------------------------------------------------+
|
||||
| | The precise rules are as follows: suppose that the |
|
||||
| | result formatted with presentation type ``'e'`` and |
|
||||
| | precision ``p-1`` would have exponent ``exp``. Then |
|
||||
| | if ``-4 <= exp < p``, the number is formatted |
|
||||
| | with presentation type ``'f'`` and precision |
|
||||
| | ``p-1-exp``. Otherwise, the number is formatted |
|
||||
| | with presentation type ``'e'`` and precision ``p-1``. |
|
||||
| | In both cases insignificant trailing zeros are removed |
|
||||
| | from the significand, and the decimal point is also |
|
||||
| | removed if there are no remaining digits following it. |
|
||||
| | |
|
||||
| | Positive and negative infinity, positive and negative |
|
||||
| | zero, and nans, are formatted as ``inf``, ``-inf``, |
|
||||
| | ``0``, ``-0`` and ``nan`` respectively, regardless of |
|
||||
| | the precision. |
|
||||
| | |
|
||||
+---------+----------------------------------------------------------+
|
||||
|
||||
The available presentation types for pointers are:
|
||||
|
||||
+---------+----------------------------------------------------------+
|
||||
| Type | Meaning |
|
||||
+=========+==========================================================+
|
||||
| ``'p'`` | Pointer format. This is the default type for |
|
||||
| | pointers and may be omitted. |
|
||||
+---------+----------------------------------------------------------+
|
||||
| none | The same as ``'p'``. |
|
||||
+---------+----------------------------------------------------------+
|
||||
|
||||
.. _chrono-specs:
|
||||
|
||||
Chrono Format Specifications
|
||||
============================
|
||||
|
||||
Format specifications for chrono types have the following syntax:
|
||||
|
||||
.. productionlist:: sf
|
||||
chrono_format_spec: [[`fill`]`align`][`width`]["." `precision`][`chrono_specs`]
|
||||
chrono_specs: [`chrono_specs`] `conversion_spec` | `chrono_specs` `literal_char`
|
||||
conversion_spec: "%" [`modifier`] `chrono_type`
|
||||
literal_char: <a character other than '{', '}' or '%'>
|
||||
modifier: "E" | "O"
|
||||
chrono_type: "a" | "A" | "b" | "B" | "c" | "C" | "d" | "D" | "e" | "F" |
|
||||
: "g" | "G" | "h" | "H" | "I" | "j" | "m" | "M" | "n" | "p" |
|
||||
: "q" | "Q" | "r" | "R" | "S" | "t" | "T" | "u" | "U" | "V" |
|
||||
: "w" | "W" | "x" | "X" | "y" | "Y" | "z" | "Z" | "%"
|
||||
|
||||
Literal chars are copied unchanged to the output. Precision is valid only for
|
||||
``std::chrono::duration`` types with a floating-point representation type.
|
||||
|
||||
The available presentation types (*chrono_type*) for chrono durations and time
|
||||
points are:
|
||||
|
||||
+---------+--------------------------------------------------------------------+
|
||||
| Type | Meaning |
|
||||
+=========+====================================================================+
|
||||
| ``'H'`` | The hour (24-hour clock) as a decimal number. If the result is a |
|
||||
| | single digit, it is prefixed with 0. The modified command ``%OH`` |
|
||||
| | produces the locale's alternative representation. |
|
||||
+---------+--------------------------------------------------------------------+
|
||||
| ``'M'`` | The minute as a decimal number. If the result is a single digit, |
|
||||
| | it is prefixed with 0. The modified command ``%OM`` produces the |
|
||||
| | locale's alternative representation. |
|
||||
+---------+--------------------------------------------------------------------+
|
||||
| ``'S'`` | Seconds as a decimal number. If the number of seconds is less than |
|
||||
| | 10, the result is prefixed with 0. If the precision of the input |
|
||||
| | cannot be exactly represented with seconds, then the format is a |
|
||||
| | decimal floating-point number with a fixed format and a precision |
|
||||
| | matching that of the precision of the input (or to a microseconds |
|
||||
| | precision if the conversion to floating-point decimal seconds |
|
||||
| | cannot be made within 18 fractional digits). The character for the |
|
||||
| | decimal point is localized according to the locale. The modified |
|
||||
| | command ``%OS`` produces the locale's alternative representation. |
|
||||
+---------+--------------------------------------------------------------------+
|
||||
|
||||
Specifiers that have a calendaric component such as `'d'` (the day of month)
|
||||
are valid only for ``std::tm`` and not durations or time points.
|
||||
|
||||
``std::tm`` uses the system's `strftime
|
||||
<https://en.cppreference.com/w/cpp/chrono/c/strftime>`_ so refer to its
|
||||
documentation for details on supported conversion specifiers.
|
||||
|
||||
.. _formatexamples:
|
||||
|
||||
Format Examples
|
||||
===============
|
||||
|
||||
This section contains examples of the format syntax and comparison with
|
||||
the printf formatting.
|
||||
|
||||
In most of the cases the syntax is similar to the printf formatting, with the
|
||||
addition of the ``{}`` and with ``:`` used instead of ``%``.
|
||||
For example, ``"%03.2f"`` can be translated to ``"{:03.2f}"``.
|
||||
|
||||
The new format syntax also supports new and different options, shown in the
|
||||
following examples.
|
||||
|
||||
Accessing arguments by position::
|
||||
|
||||
fmt::format("{0}, {1}, {2}", 'a', 'b', 'c');
|
||||
// Result: "a, b, c"
|
||||
fmt::format("{}, {}, {}", 'a', 'b', 'c');
|
||||
// Result: "a, b, c"
|
||||
fmt::format("{2}, {1}, {0}", 'a', 'b', 'c');
|
||||
// Result: "c, b, a"
|
||||
fmt::format("{0}{1}{0}", "abra", "cad"); // arguments' indices can be repeated
|
||||
// Result: "abracadabra"
|
||||
|
||||
Aligning the text and specifying a width::
|
||||
|
||||
fmt::format("{:<30}", "left aligned");
|
||||
// Result: "left aligned "
|
||||
fmt::format("{:>30}", "right aligned");
|
||||
// Result: " right aligned"
|
||||
fmt::format("{:^30}", "centered");
|
||||
// Result: " centered "
|
||||
fmt::format("{:*^30}", "centered"); // use '*' as a fill char
|
||||
// Result: "***********centered***********"
|
||||
|
||||
Dynamic width::
|
||||
|
||||
fmt::format("{:<{}}", "left aligned", 30);
|
||||
// Result: "left aligned "
|
||||
|
||||
Dynamic precision::
|
||||
|
||||
fmt::format("{:.{}f}", 3.14, 1);
|
||||
// Result: "3.1"
|
||||
|
||||
Replacing ``%+f``, ``%-f``, and ``% f`` and specifying a sign::
|
||||
|
||||
fmt::format("{:+f}; {:+f}", 3.14, -3.14); // show it always
|
||||
// Result: "+3.140000; -3.140000"
|
||||
fmt::format("{: f}; {: f}", 3.14, -3.14); // show a space for positive numbers
|
||||
// Result: " 3.140000; -3.140000"
|
||||
fmt::format("{:-f}; {:-f}", 3.14, -3.14); // show only the minus -- same as '{:f}; {:f}'
|
||||
// Result: "3.140000; -3.140000"
|
||||
|
||||
Replacing ``%x`` and ``%o`` and converting the value to different bases::
|
||||
|
||||
fmt::format("int: {0:d}; hex: {0:x}; oct: {0:o}; bin: {0:b}", 42);
|
||||
// Result: "int: 42; hex: 2a; oct: 52; bin: 101010"
|
||||
// with 0x or 0 or 0b as prefix:
|
||||
fmt::format("int: {0:d}; hex: {0:#x}; oct: {0:#o}; bin: {0:#b}", 42);
|
||||
// Result: "int: 42; hex: 0x2a; oct: 052; bin: 0b101010"
|
||||
|
||||
Padded hex byte with prefix and always prints both hex characters::
|
||||
|
||||
fmt::format("{:#04x}", 0);
|
||||
// Result: "0x00"
|
||||
|
||||
Box drawing using Unicode fill::
|
||||
|
||||
fmt::print(
|
||||
"┌{0:─^{2}}┐\n"
|
||||
"│{1: ^{2}}│\n"
|
||||
"└{0:─^{2}}┘\n", "", "Hello, world!", 20);
|
||||
|
||||
prints::
|
||||
|
||||
┌────────────────────┐
|
||||
│ Hello, world! │
|
||||
└────────────────────┘
|
||||
|
||||
Using type-specific formatting::
|
||||
|
||||
#include <fmt/chrono.h>
|
||||
|
||||
auto t = tm();
|
||||
t.tm_year = 2010 - 1900;
|
||||
t.tm_mon = 7;
|
||||
t.tm_mday = 4;
|
||||
t.tm_hour = 12;
|
||||
t.tm_min = 15;
|
||||
t.tm_sec = 58;
|
||||
fmt::print("{:%Y-%m-%d %H:%M:%S}", t);
|
||||
// Prints: 2010-08-04 12:15:58
|
||||
|
||||
Using the comma as a thousands separator::
|
||||
|
||||
#include <fmt/locale.h>
|
||||
|
||||
auto s = fmt::format(std::locale("en_US.UTF-8"), "{:L}", 1234567890);
|
||||
// s == "1,234,567,890"
|
||||
|
||||
.. ifconfig:: False
|
||||
|
||||
Nesting arguments and more complex examples::
|
||||
|
||||
>>> for align, text in zip('<^>', ['left', 'center', 'right']):
|
||||
... '{0:{fill}{align}16}") << text, fill=align, align=align)
|
||||
...
|
||||
'left<<<<<<<<<<<<'
|
||||
'^^^^^center^^^^^'
|
||||
'>>>>>>>>>>>right'
|
||||
>>>
|
||||
>>> octets = [192, 168, 0, 1]
|
||||
Format("{:02X}{:02X}{:02X}{:02X}") << *octets)
|
||||
'C0A80001'
|
||||
>>> int(_, 16)
|
||||
3232235521
|
||||
>>>
|
||||
>>> width = 5
|
||||
>>> for num in range(5,12):
|
||||
... for base in 'dXob':
|
||||
... print('{0:{width}{base}}") << num, base=base, width=width), end=' ')
|
||||
... print()
|
||||
...
|
||||
5 5 5 101
|
||||
6 6 6 110
|
||||
7 7 7 111
|
||||
8 8 10 1000
|
||||
9 9 11 1001
|
||||
10 A 12 1010
|
||||
11 B 13 1011
|
||||
+212
@@ -0,0 +1,212 @@
|
||||
*****
|
||||
Usage
|
||||
*****
|
||||
|
||||
To use the {fmt} library, add :file:`fmt/core.h`, :file:`fmt/format.h`,
|
||||
:file:`fmt/format-inl.h`, :file:`src/format.cc` and optionally other headers
|
||||
from a `release archive <https://github.com/fmtlib/fmt/releases/latest>`_ or
|
||||
the `Git repository <https://github.com/fmtlib/fmt>`_ to your project.
|
||||
Alternatively, you can :ref:`build the library with CMake <building>`.
|
||||
|
||||
.. _building:
|
||||
|
||||
Building the Library
|
||||
====================
|
||||
|
||||
The included `CMake build script`__ can be used to build the fmt
|
||||
library on a wide range of platforms. CMake is freely available for
|
||||
download from https://www.cmake.org/download/.
|
||||
|
||||
__ https://github.com/fmtlib/fmt/blob/master/CMakeLists.txt
|
||||
|
||||
CMake works by generating native makefiles or project files that can
|
||||
be used in the compiler environment of your choice. The typical
|
||||
workflow starts with::
|
||||
|
||||
mkdir build # Create a directory to hold the build output.
|
||||
cd build
|
||||
cmake .. # Generate native build scripts.
|
||||
|
||||
where :file:`{<path/to/fmt>}` is a path to the ``fmt`` repository.
|
||||
|
||||
If you are on a \*nix system, you should now see a Makefile in the
|
||||
current directory. Now you can build the library by running :command:`make`.
|
||||
|
||||
Once the library has been built you can invoke :command:`make test` to run
|
||||
the tests.
|
||||
|
||||
You can control generation of the make ``test`` target with the ``FMT_TEST``
|
||||
CMake option. This can be useful if you include fmt as a subdirectory in
|
||||
your project but don't want to add fmt's tests to your ``test`` target.
|
||||
|
||||
If you use Windows and have Visual Studio installed, a :file:`FMT.sln`
|
||||
file and several :file:`.vcproj` files will be created. You can then build them
|
||||
using Visual Studio or msbuild.
|
||||
|
||||
On Mac OS X with Xcode installed, an :file:`.xcodeproj` file will be generated.
|
||||
|
||||
To build a `shared library`__ set the ``BUILD_SHARED_LIBS`` CMake variable to
|
||||
``TRUE``::
|
||||
|
||||
cmake -DBUILD_SHARED_LIBS=TRUE ...
|
||||
|
||||
__ https://en.wikipedia.org/wiki/Library_%28computing%29#Shared_libraries
|
||||
|
||||
|
||||
To build a `static library` with position independent code (required if the main
|
||||
consumer of the fmt library is a shared library i.e. a Python extension) set the
|
||||
``CMAKE_POSITION_INDEPENDENT_CODE`` CMake variable to ``TRUE``::
|
||||
|
||||
cmake -DCMAKE_POSITION_INDEPENDENT_CODE=TRUE ...
|
||||
|
||||
|
||||
Installing the Library
|
||||
======================
|
||||
|
||||
After building the library you can install it on a Unix-like system by running
|
||||
:command:`sudo make install`.
|
||||
|
||||
Usage with CMake
|
||||
================
|
||||
|
||||
You can add the ``fmt`` library directory into your project and include it in
|
||||
your ``CMakeLists.txt`` file::
|
||||
|
||||
add_subdirectory(fmt)
|
||||
|
||||
or
|
||||
|
||||
::
|
||||
|
||||
add_subdirectory(fmt EXCLUDE_FROM_ALL)
|
||||
|
||||
to exclude it from ``make``, ``make all``, or ``cmake --build .``.
|
||||
|
||||
You can detect and use an installed version of {fmt} as follows::
|
||||
|
||||
find_package(fmt)
|
||||
target_link_libraries(<your-target> fmt::fmt)
|
||||
|
||||
Setting up your target to use a header-only version of ``fmt`` is equally easy::
|
||||
|
||||
target_link_libraries(<your-target> PRIVATE fmt::fmt-header-only)
|
||||
|
||||
Usage with build2
|
||||
=================
|
||||
|
||||
You can use `build2 <https://build2.org>`_, a dependency manager and a
|
||||
build-system combined, to use ``fmt``.
|
||||
|
||||
Currently this package is available in these package repositories:
|
||||
|
||||
- **https://cppget.org/fmt/** for released and published versions.
|
||||
- `The git repository with the sources of the build2 package of fmt <https://github.com/build2-packaging/fmt.git>`_
|
||||
for unreleased or custom revisions of ``fmt``.
|
||||
|
||||
**Usage:**
|
||||
|
||||
- ``build2`` package name: ``fmt``
|
||||
- Library target name : ``lib{fmt}``
|
||||
|
||||
For example, to make your ``build2`` project depend on ``fmt``:
|
||||
|
||||
- Add one of the repositories to your configurations, or in your
|
||||
``repositories.manifest``, if not already there::
|
||||
|
||||
:
|
||||
role: prerequisite
|
||||
location: https://pkg.cppget.org/1/stable
|
||||
|
||||
- Add this package as a dependency to your ``./manifest`` file
|
||||
(example for ``v7.0.x``)::
|
||||
|
||||
depends: fmt ~7.0.0
|
||||
|
||||
- Import the target and use it as a prerequisite to your own target
|
||||
using `fmt` in the appropriate ``buildfile``::
|
||||
|
||||
import fmt = fmt%lib{fmt}
|
||||
lib{mylib} : cxx{**} ... $fmt
|
||||
|
||||
Then build your project as usual with `b` or `bdep update`.
|
||||
|
||||
For ``build2`` newcomers or to get more details and use cases, you can read the
|
||||
``build2``
|
||||
`toolchain introduction <https://build2.org/build2-toolchain/doc/build2-toolchain-intro.xhtml>`_.
|
||||
|
||||
Building the Documentation
|
||||
==========================
|
||||
|
||||
To build the documentation you need the following software installed on your
|
||||
system:
|
||||
|
||||
* `Python <https://www.python.org/>`_ with pip and virtualenv
|
||||
* `Doxygen <http://www.stack.nl/~dimitri/doxygen/>`_
|
||||
* `Less <http://lesscss.org/>`_ with ``less-plugin-clean-css``.
|
||||
Ubuntu doesn't package the ``clean-css`` plugin so you should use ``npm``
|
||||
instead of ``apt`` to install both ``less`` and the plugin::
|
||||
|
||||
sudo npm install -g less less-plugin-clean-css.
|
||||
|
||||
First generate makefiles or project files using CMake as described in
|
||||
the previous section. Then compile the ``doc`` target/project, for example::
|
||||
|
||||
make doc
|
||||
|
||||
This will generate the HTML documentation in ``doc/html``.
|
||||
|
||||
Conda
|
||||
=====
|
||||
|
||||
fmt can be installed on Linux, macOS and Windows with
|
||||
`Conda <https://docs.conda.io/en/latest/>`__, using its
|
||||
`conda-forge <https://conda-forge.org>`__
|
||||
`package <https://github.com/conda-forge/fmt-feedstock>`__, as follows::
|
||||
|
||||
conda install -c conda-forge fmt
|
||||
|
||||
Vcpkg
|
||||
=====
|
||||
|
||||
You can download and install fmt using the `vcpkg
|
||||
<https://github.com/Microsoft/vcpkg>`__ dependency manager::
|
||||
|
||||
git clone https://github.com/Microsoft/vcpkg.git
|
||||
cd vcpkg
|
||||
./bootstrap-vcpkg.sh
|
||||
./vcpkg integrate install
|
||||
./vcpkg install fmt
|
||||
|
||||
The fmt port in vcpkg is kept up to date by Microsoft team members and community
|
||||
contributors. If the version is out of date, please `create an issue or pull
|
||||
request <https://github.com/Microsoft/vcpkg>`__ on the vcpkg repository.
|
||||
|
||||
LHelper
|
||||
=======
|
||||
|
||||
You can download and install fmt using
|
||||
`lhelper <https://github.com/franko/lhelper>`__ dependency manager::
|
||||
|
||||
lhelper activate <some-environment>
|
||||
lhelper install fmt
|
||||
|
||||
All the recipes for lhelper are kept in the
|
||||
`lhelper's recipe <https://github.com/franko/lhelper-recipes>`__ repository.
|
||||
|
||||
Android NDK
|
||||
===========
|
||||
|
||||
fmt provides `Android.mk file`__ that can be used to build the library
|
||||
with `Android NDK <https://developer.android.com/tools/sdk/ndk/index.html>`_.
|
||||
For an example of using fmt with Android NDK, see the
|
||||
`android-ndk-example <https://github.com/fmtlib/android-ndk-example>`_
|
||||
repository.
|
||||
|
||||
__ https://github.com/fmtlib/fmt/blob/master/support/Android.mk
|
||||
|
||||
Homebrew
|
||||
========
|
||||
|
||||
fmt can be installed on OS X using `Homebrew <https://brew.sh/>`_::
|
||||
|
||||
brew install fmt
|
||||
Reference in New Issue
Block a user