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Document user-defined literals

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Dean Moldovan 2015-10-11 02:34:20 +02:00
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doc/index.rst
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@ -65,6 +65,34 @@ The Format API also supports positional arguments useful for localization:
fmt::print("I'd rather be {1} than {0}.", "right", "happy");
Named arguments can be created with ``fmt::arg``. This makes it easier to track
what goes where when multiple values are being inserted:
.. 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++
fmt::print("Hello, {name}! The answer is {number}. Goodbye, {name}.",
"name"_a="World", "number"_a=42);
The ``_format`` suffix may be used to format string literals similar to Python:
.. code:: c++
std::string message = "{0}{1}{0}"_format("abra", "cad");
Other than the placement of the format string on the left of the operator,
``_format`` is functionally identical to ``fmt::format``. In order to use the
literal operators, they must be made visible with the directive
``using namespace fmt::literals;``. Note that this brings in only ``_a`` and
``_format`` but nothing else from the ``fmt`` namespace.
.. _write-api:
Write API
@ -128,13 +156,22 @@ compilers where it has been tested and known to work:
* Mac OS X with GCC 4.2.1 and Clang 4.2, 5.1.0
* 64-bit Windows with Visual C++ 2010 and
`2013 <https://ci.appveyor.com/project/vitaut/cppformat>`_
* 64-bit Windows with Visual C++ 2010, 2013 and
`2015 <https://ci.appveyor.com/project/vitaut/cppformat>`_
* 32-bit Windows with Visual C++ 2010
Although the library uses C++11 features when available, it also works with older
compilers and standard library implementations.
compilers and standard library implementations. The only thing to keep in mind
for C++98 portability:
* Variadic templates: minimum GCC 4.4, Clang 2.9 or VS2013. This feature allow
the Format API to accept an unlimited number of arguments. With older compilers
the maximum is 15.
* User-defined literals: minimum GCC 4.7, Clang 3.1 or VS2015. The suffixes
``_format`` and ``_a`` are functionally equivalent to the functions
``fmt::format`` and ``fmt::arg``.
The output of all formatting functions is consistent across platforms. In particular,
formatting a floating-point infinity always gives ``inf`` while the output