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"Grammar" chapter refactored and "Default formatting" chapter added

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Mateusz Pusz
2020-03-17 15:26:53 +01:00
parent 814a620fbb
commit 1bb484e1c4
1 changed files with 17 additions and 4 deletions
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docs/framework/text_output.rst
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@@ -32,15 +32,28 @@ of an unknown ``auto`` type before passing it to the text output::
Formatting the output
---------------------
Grammar:
^^^^^^^^
Grammar
^^^^^^^
.. productionlist::
units-format-spec: fill-and-align[opt] sign[opt] width[opt] precision[opt] type[opt] units-specs[opt]
units-format-spec: [fill-and-align] [sign] [width] [precision] [type] [units-specs]
units-specs: conversion-spec
: units-specs conversion-spec
: units-specs literal-char
literal-char: any character other than '{' or '}'
conversion-spec: '%' modifier[opt] units-type
conversion-spec: '%' [modifier] units-type
modifier: 'A'
units-type: one of 'n', 'q', 'Q', 't', '%'
Default formatting
^^^^^^^^^^^^^^^^^^
To format `quantity` values the formatting facility uses :token:`units-format-spec`.
In case it is left empty the default formatting of ``{:%Q %q}`` is applied. The same
default formatting is also applied to output streams. This is why the following lines
produce the same output::
std::cout << "Distance: " << 123q_km << "\n";
fmt::print("Distance: {}\n", 123q_km);
fmt::print("Distance: {:%Q %q}\n", 123q_km);