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Victor Zverovich
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doc/api.rst
259
doc/api.rst
@ -4,14 +4,29 @@
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API Reference
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*************
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All functions and classes provided by the {fmt} library reside in namespace
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``fmt`` and macros have prefix ``FMT_``.
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The {fmt} library API consists of the following parts:
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Format API
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==========
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* :ref:`fmt/core.h <core-api>`: the core API providing argument handling
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facilities and a lightweight subset of formatting functions
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* :ref:`fmt/format.h <format-api>`: the full format API providing compile-time
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format string checks, output iterator and user-defined type support
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* :ref:`fmt/time.h <time-api>`: date and time formatting
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* :ref:`fmt/ostream.h <ostream-api>`: ``std::ostream`` support
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* :ref:`fmt/printf.h <printf-api>`: ``printf`` formatting
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The following functions defined in ``fmt/core.h`` use :ref:`format string
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syntax <syntax>` similar to that of Python's `str.format
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All functions and types provided by the library reside in namespace ``fmt`` and
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macros have prefix ``FMT_`` or ``fmt``.
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.. _core-api:
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Core API
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========
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``fmt/core.h`` defines the core API which provides argument handling facilities
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and a lightweight subset of formatting functions.
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The following functions use :ref:`format string syntax <syntax>`
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imilar to that of Python's `str.format
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<http://docs.python.org/3/library/stdtypes.html#str.format>`_.
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They take *format_str* and *args* as arguments.
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@ -21,35 +36,52 @@ arguments in the resulting string.
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*args* is an argument list representing objects to be formatted.
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The `performance of the formating functions
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<https://github.com/fmtlib/fmt/blob/master/README.rst#speed-tests>`_ is close
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to that of glibc's ``printf`` and better than the performance of IOStreams.
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.. _format:
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.. doxygenfunction:: format(string_view, const Args&...)
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.. doxygenfunction:: vformat(string_view, format_args)
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.. _print:
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.. doxygenfunction:: print(string_view, const Args&...)
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.. doxygenfunction:: vprint(string_view, format_args)
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.. doxygenfunction:: print(std::FILE *, string_view, const Args&...)
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.. doxygenfunction:: vprint(std::FILE *, string_view, format_args)
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Date and time formatting
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------------------------
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.. _format-api:
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The library supports `strftime
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<http://en.cppreference.com/w/cpp/chrono/c/strftime>`_-like date and time
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formatting::
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Named arguments
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---------------
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#include "fmt/time.h"
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.. doxygenfunction:: fmt::arg(string_view, const T&)
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std::time_t t = std::time(nullptr);
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// Prints "The date is 2016-04-29." (with the current date)
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fmt::print("The date is {:%Y-%m-%d}.", *std::localtime(&t));
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Argument lists
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--------------
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The format string syntax is described in the documentation of
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`strftime <http://en.cppreference.com/w/cpp/chrono/c/strftime>`_.
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.. doxygenclass:: fmt::basic_format_args
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:members:
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.. doxygenstruct:: fmt::format_args
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.. doxygenfunction:: fmt::make_args(const Args&...)
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Compatibility
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-------------
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.. doxygenclass:: fmt::basic_string_view
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:members:
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Format API
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==========
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``fmt/format.h`` defines the full format API providing compile-time format
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string checks, output iterator and user-defined type support.
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Compile-time format string checks
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---------------------------------
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.. doxygendefine:: fmt
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Formatting user-defined types
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-----------------------------
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@ -57,6 +89,8 @@ Formatting user-defined types
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To make a user-defined type formattable, specialize the ``formatter<T>`` struct
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template and implement ``parse`` and ``format`` methods::
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#include <fmt/format.h>
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struct point { double x, y; };
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namespace fmt {
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@ -88,28 +122,10 @@ This section shows how to define a custom format function for a user-defined
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type. The next section describes how to get ``fmt`` to use a conventional stream
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output ``operator<<`` when one is defined for a user-defined type.
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``std::ostream`` support
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------------------------
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Output iterator support
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-----------------------
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The header ``fmt/ostream.h`` provides ``std::ostream`` support including
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formatting of user-defined types that have overloaded ``operator<<``::
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#include "fmt/ostream.h"
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class date {
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int year_, month_, day_;
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public:
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date(int year, int month, int day): year_(year), month_(month), day_(day) {}
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friend std::ostream &operator<<(std::ostream &os, const date &d) {
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return os << d.year_ << '-' << d.month_ << '-' << d.day_;
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}
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};
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std::string s = fmt::format("The date is {}", date(2012, 12, 9));
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// s == "The date is 2012-12-9"
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.. doxygenfunction:: print(std::ostream&, string_view, const Args&...)
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.. doxygenfunction:: fmt::format_to(OutputIt, string_view, const Args&...)
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Literal-based API
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-----------------
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@ -120,6 +136,57 @@ The following user-defined literals are defined in ``fmt/format.h``.
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.. doxygenfunction:: operator""_a(const char *, std::size_t)
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Utilities
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---------
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.. doxygenfunction:: fmt::to_string(const T&)
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.. doxygenclass:: fmt::basic_memory_buffer
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:protected-members:
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:members:
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System errors
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-------------
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.. doxygenclass:: fmt::system_error
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:members:
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.. doxygenfunction:: fmt::format_system_error
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.. doxygenclass:: fmt::windows_error
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:members:
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.. _formatstrings:
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Custom allocators
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-----------------
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The {fmt} library supports custom dynamic memory allocators.
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A custom allocator class can be specified as a template argument to
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:class:`fmt::basic_memory_buffer`::
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using custom_memory_buffer =
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fmt::basic_memory_buffer<char, fmt::inline_buffer_size, custom_allocator>;
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It is also possible to write a formatting function that uses a custom
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allocator::
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using custom_string =
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std::basic_string<char, std::char_traits<char>, custom_allocator>;
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custom_string vformat(custom_allocator alloc, fmt::string_view format_str,
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fmt::format_args args) {
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custom_memory_buffer buf(alloc);
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fmt::vformat_to(buf, format_str, args);
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return custom_string(buf.data(), buf.size(), alloc);
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}
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template <typename ...Args>
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inline custom_string format(custom_allocator alloc,
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fmt::string_view format_str,
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const Args & ... args) {
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return vformat(alloc, format_str, fmt::make_args(args...));
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}
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Custom formatting of built-in types
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-----------------------------------
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@ -170,8 +237,53 @@ custom argument formatter class::
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.. doxygenclass:: fmt::arg_formatter
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:members:
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Printf formatting
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-----------------
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.. _time-api:
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Date and time formatting
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========================
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The library supports `strftime
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<http://en.cppreference.com/w/cpp/chrono/c/strftime>`_-like date and time
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formatting::
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#include <fmt/time.h>
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std::time_t t = std::time(nullptr);
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// Prints "The date is 2016-04-29." (with the current date)
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fmt::print("The date is {:%Y-%m-%d}.", *std::localtime(&t));
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The format string syntax is described in the documentation of
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`strftime <http://en.cppreference.com/w/cpp/chrono/c/strftime>`_.
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.. _ostream-api:
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``std::ostream`` support
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========================
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``fmt/ostream.h`` provides ``std::ostream`` support including formatting of
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user-defined types that have overloaded ``operator<<``::
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#include <fmt/ostream.h>
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class date {
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int year_, month_, day_;
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public:
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date(int year, int month, int day): year_(year), month_(month), day_(day) {}
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friend std::ostream &operator<<(std::ostream &os, const date &d) {
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return os << d.year_ << '-' << d.month_ << '-' << d.day_;
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}
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};
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std::string s = fmt::format("The date is {}", date(2012, 12, 9));
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// s == "The date is 2012-12-9"
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.. doxygenfunction:: print(std::ostream&, string_view, const Args&...)
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.. _printf-api:
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``printf`` formatting
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=====================
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The header ``fmt/printf.h`` provides ``printf``-like formatting functionality.
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The following functions use `printf format string syntax
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@ -220,62 +332,3 @@ store output elsewhere by subclassing `~fmt::BasicWriter`.
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.. doxygenfunction:: pad(int, unsigned, Char)
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Utilities
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=========
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.. doxygenfunction:: fmt::arg(string_view, const T&)
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.. doxygenclass:: fmt::basic_format_args
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:members:
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.. doxygenfunction:: fmt::to_string(const T&)
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.. doxygenclass:: fmt::basic_string_view
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:members:
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.. doxygenclass:: fmt::basic_memory_buffer
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:protected-members:
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:members:
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System errors
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=============
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.. doxygenclass:: fmt::system_error
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:members:
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.. doxygenfunction:: fmt::format_system_error
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.. doxygenclass:: fmt::windows_error
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:members:
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.. _formatstrings:
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Custom allocators
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=================
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The {fmt} library supports custom dynamic memory allocators.
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A custom allocator class can be specified as a template argument to
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:class:`fmt::basic_memory_buffer`::
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using custom_memory_buffer =
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fmt::basic_memory_buffer<char, fmt::inline_buffer_size, custom_allocator>;
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It is also possible to write a formatting function that uses a custom
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allocator::
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using custom_string =
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std::basic_string<char, std::char_traits<char>, custom_allocator>;
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custom_string vformat(custom_allocator alloc, fmt::string_view format_str,
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fmt::format_args args) {
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custom_memory_buffer buf(alloc);
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fmt::vformat_to(buf, format_str, args);
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return custom_string(buf.data(), buf.size(), alloc);
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}
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template <typename ...Args>
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inline custom_string format(custom_allocator alloc,
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fmt::string_view format_str,
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const Args & ... args) {
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return vformat(alloc, format_str, fmt::make_args(args...));
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}
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@ -1069,7 +1069,8 @@ class basic_format_args {
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}
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};
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// This is a separate type rather than a typedef to make symbols readable.
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/** An alias to ``basic_format_args<context>``. */
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// It is a separate type rather than a typedef to make symbols readable.
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struct format_args: basic_format_args<context> {
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template <typename ...Args>
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format_args(Args && ... arg)
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@ -1179,7 +1180,7 @@ std::wstring vformat(wstring_view format_str, wformat_args args);
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**Example**::
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#include "fmt/core.h"
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#include <fmt/core.h>
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std::string message = fmt::format("The answer is {}", 42);
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\endrst
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*/
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@ -3315,7 +3315,7 @@ auto join(const Range &range, wstring_view sep)
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**Example**::
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#include "fmt/format.h"
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#include <fmt/format.h>
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std::string answer = fmt::to_string(42);
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\endrst
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@ -3528,6 +3528,16 @@ operator"" _a(const wchar_t *s, std::size_t) { return {s}; }
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}()
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#ifndef FMT_NO_FMT_STRING_ALIAS
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/**
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\rst
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Constructs a compile-time format string.
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**Example**::
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#include <fmt/format.h>
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std::string s = fmt::format(fmt("{:d}"), "foo"); // fails to compile
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\endrst
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*/
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# define fmt(s) FMT_STRING(s)
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#endif
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