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Victor Zverovich 2016-10-06 07:38:19 -07:00
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commit 4809e2956a
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doc/api.rst
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@ -58,29 +58,26 @@ formatting::
The format string syntax is described in the documentation of
`strftime <http://en.cppreference.com/w/cpp/chrono/c/strftime>`_.
Formatting User-Defined types
Formatting user-defined types
-----------------------------
A custom ``format_arg`` function may be implemented and used to format any user-
defined type. That is how date and time formatting described in the previous
section is implemented in :file:`fmt/time.h`. The following example shows how to implement custom formatting for a user-defined structure.
A custom ``format_arg`` function may be implemented and used to format any
user-defined type. That is how date and time formatting described in the
previous section is implemented in :file:`fmt/time.h`. The following example
shows how to implement custom formatting for a user-defined structure.
::
struct MyStruct { double a, b, c, d; };
struct MyStruct { double a, b; };
void format_arg(fmt::BasicFormatter<char> &f,
const char *&format_str, const MyStruct &s) {
f.writer().write("[MyStruct: a={:.1f}, b={:.2f}, c={:.3f}, d={:.4f}]",
s.a, s.b, s.c, s.d);
const char *&format_str, const MyStruct &s) {
f.writer().write("[MyStruct: a={:.1f}, b={:.2f}]", s.a, s.b);
}
void f()
{
MyStruct m = { 1, 2, 3, 4 };
std::string s = fmt::format("m={}", n);
// s == "m=[MyStruct: a=1.0, b=2.00, c=3.000, d=4.0000]"
}
MyStruct m = { 1, 2 };
std::string s = fmt::format("m={}", n);
// s == "m=[MyStruct: a=1.0, b=2.00]"
Note in the example above the ``format_arg`` function ignores the contents of
``format_str`` so the type will always be formatted as specified. See