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<h1>Text Formatting</h1>
<p>
2016-08-19
</p>
<address>
Victor Zverovich, victor.zverovich@gmail.com
</address>
<div id="toc"></div>
<h2><a name="Introduction">Introduction</a></h2>
<p>
This paper proposes a new text formatting functionality that can be used as a
safe and extensible alternative to the <code>printf</code> family of functions.
It is intended to complement the existing C++ I/O streams library and reuse
some of its infrastructure such as overloaded insertion operators for
user-defined types.
</p>
<p>
Example:
<pre class="example">
<code>std::string message = std::format("The answer is {}.", 42);</code>
</pre>
<h2><a name="Design">Design</a></h2>
<h3><a name="Syntax">Format String Syntax</a></h3>
<p>
Variations of the printf format string syntax are arguably the most popular
among the programming languages and C++ itself inherits <code>printf</code>
from C <a href="#1">[1]</a>. The advantage of the printf syntax is that many
programmers are familiar with it. However, in its current form it has a number
of issues:
</p>
<ul>
<li>Many format specifiers like <code>hh</code>, <code>h</code>, <code>l</code>,
<code>j</code>, etc. are used only to convey type information.
They are redundant in type-safe formatting and would unnecessarily
complicate specification and parsing.</li>
<li>There is no standard way to extend the syntax for user-defined types.</li>
<li>There are subtle differences between different implementations. For example,
POSIX positional arguments <a href="#2">[2]</a> are not supported on
some systems <a href="#6">[6]</a>.</li>
<li>Using <code>'%'</code> in a custom format specifier, e.g. for
<code>put_time</code>-like time formatting, poses difficulties.</li>
</ul>
<p>
Although it is possible to address these issues, this will break compatibility
and can potentially be more confusing to users than introducing a different
syntax.
</p>
<p>
Therefore we propose a new syntax based on the ones used in Python
<a href="#3">[3]</a>, the .NET family of languages <a href="#4">[4]</a>,
and Rust <a href="#5">[5]</a>. This syntax employs <code>'{'</code> and
<code>'}'</code> as replacement field delimiters instead of <code>'%'</code>
and it is described in details in the <a href="#SyntaxRef">syntax reference</a>.
Here are some of the advantages:
</p>
<ul>
<li>Consistent and easy to parse mini-language focused on formatting rather
than conveying type information</li>
<li>Extensibility and support for custom format strings for user-defined
types</li>
<li>Positional arguments</li>
<li>Support for both locale-specific and locale-independent formatting (see
<a href="#Locale">Locale Support</a>)</li>
<li>Formatting improvements such as better alignment control, fill character,
and binary format
</ul>
<p>
The syntax is expressive enough to enable translation, possibly automated,
of most printf format strings. The correspondence between <code>printf</code>
and the new syntax is given in the following table.
</p>
<table>
<thead>
<tr><th>printf</th><th>new</th></tr>
</thead>
<tbody>
<tr><td>-</td><td>&lt;</td></tr>
<tr><td>+</td><td>+</td></tr>
<tr><td><em>space</em></td><td><em>space</em></td></tr>
<tr><td>#</td><td>#</td></tr>
<tr><td>0</td><td>0</td></tr>
<tr><td>hh</td><td>unused</td></tr>
<tr><td>h</td><td>unused</td></tr>
<tr><td>l</td><td>unused</td></tr>
<tr><td>ll</td><td>unused</td></tr>
<tr><td>j</td><td>unused</td></tr>
<tr><td>z</td><td>unused</td></tr>
<tr><td>t</td><td>unused</td></tr>
<tr><td>L</td><td>unused</td></tr>
<tr><td>c</td><td>c (optional)</td></tr>
<tr><td>s</td><td>s (optional)</td></tr>
<tr><td>d</td><td>d (optional)</td></tr>
<tr><td>i</td><td>d (optional)</td></tr>
<tr><td>o</td><td>o</td></tr>
<tr><td>x</td><td>x</td></tr>
<tr><td>X</td><td>X</td></tr>
<tr><td>u</td><td>d (optional)</td></tr>
<tr><td>f</td><td>f</td></tr>
<tr><td>F</td><td>F</td></tr>
<tr><td>e</td><td>e</td></tr>
<tr><td>E</td><td>E</td></tr>
<tr><td>a</td><td>a</td></tr>
<tr><td>A</td><td>A</td></tr>
<tr><td>g</td><td>g (optional)</td></tr>
<tr><td>G</td><td>G</td></tr>
<tr><td>n</td><td>unused</td></tr>
<tr><td>p</td><td>p (optional)</td></tr>
</tbody>
</table>
<p>
Width and precision are represented similarly in <code>printf</code> and the
proposed syntax with the only difference that runtime value is specified by
<code>*</code> in the former and <code>{}</code> in the latter, possibly with
the index of the argument inside the braces.
</p>
<p>
As can be seen from the table above, most of the specifiers remain the same
which simplifies migration from <code>printf</code>. Notable difference is
in the alignment specification. The proposed syntax allows left, center,
and right alignment represented by <code>'&lt;'</code>, <code>'^'</code>,
and <code>'&gt;'</code> respectively which is more expressive than the
corresponding <code>printf</code> syntax. The latter only supports left and
right (the default) alignment.
</p>
<p>
The following example uses center alignment and <code>'*'</code> as a fill
character:
</p>
<pre class="example">
<code>std::format("{:*^30}", "centered");</code>
</pre>
<p>
resulting in <code>"***********centered***********"</code>.
The same formatting cannot be easily achieved with <code>printf</code>.
</p>
<h3><a name="Extensibility">Extensibility</a></h3>
<p>
Both the format string syntax and the API are designed with extensibility in
mind. The mini-language can be extended for user-defined types and users can
provide functions that do parsing and formatting for such types.
</p>
<p>The general syntax of a replacement field in a format string is
<pre>
<code>replacement-field ::= '{' [arg-id] [':' format-spec] '}'</code>
</pre>
<p>
where <code>format-spec</code> is predefined for built-in types, but can be
customized for user-defined types. For example, the syntax can be extended
for <code>put_time</code>-like date and time formatting
</p>
<pre class="example">
<code>std::time_t t = std::time(nullptr);
std::string date = std::format("The date is {0:%Y-%m-%d}.", *std::localtime(&amp;t));</code>
</pre>
<p>by providing an overload of <code>std::format_arg</code> for
<code>std::tm</code>:</p>
<p>TODO: example</p>
<h3><a name="Safety">Safety</a></h3>
<p>
Formatting functions rely on variadic templates instead of the mechanism
provided by <code>&lt;cstdarg&gt;</code>. The type information is captured
automatically and passed to formatters guaranteeing type safety and making
many of the <code>printf</code> specifiers redundant (see <a href="#Syntax">
Format String Syntax</a>). Buffer management is also automatic to prevent
buffer overflow errors common to <code>printf</code>.
</p>
<h3><a name="Locale">Locale Support</a></h3>
<p>
As pointed out in
<a href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2016/p0067r1.html">
P0067R1: Elementary string conversions</a> there is a number of use
cases that do not require internationalization support, but do require high
throughput when produced by a server. These include various text-based
interchange formats such as JSON or XML. The need for locale-independent
functions for conversions between integers and strings and between
floating-point numbers and strings has also been highlighted in
<a href="http://open-std.org/JTC1/SC22/WG21/docs/papers/2015/n4412.html">
N4412: Shortcomings of iostreams</a>. Therefore a user should be able to
easily control whether to use locales or not during formatting.
</p>
<p>
We follow Python's approach <a href="#3">[3]</a> and designate a separate format
specifier <code>'n'</code> for locale-aware numeric formatting. It applies to
all integral and floating-point types. All other specifiers produce output
unaffected by locale settings. This can also have positive peformance effect
because locale-independent formatting can be implemented more efficiently.
</p>
<h3><a name="PosArguments">Positional Arguments</a></h3>
<p>
An important feature for localization is the ability to rearrange formatting
arguments because the word order may vary in different languages
<a href="#3">[3]</a>. For example:
</p>
<pre class="example">
<code>printf("String `%s' has %d characters\n", string, length(string)));</code>
</pre>
<p>A possible German translation of the format string might be:</p>
<pre class="example">
<code>"%2$d Zeichen lang ist die Zeichenkette `%1$s'\n"</code>
</pre>
<p>
using POSIX positional arguments <a href="#2">[2]</a>. Unfortunately these
positional specifiers are not portable <a href="#6">[6]</a>. The C++ I/O
streams don't support such rearranging of arguments by design because they
are interleaved with the portions of the literal string:
</p>
<pre class="example">
<code>std::cout << "String `" << string << "' has " << length(string) << " characters\n";</code>
</pre>
<p>
The current proposal allows both positional and automatically numbered
arguments, for example:
</p>
<pre class="example">
<code>std::format("String `{}' has {} characters\n", string, length(string)));</code>
</pre>
<p>with the German translation of the format string:</p>
<pre class="example">
<code>"{1} Zeichen lang ist die Zeichenkette `{0}'\n"</code>
</pre>
<h3><a name="Locale">Performance</a></h3>
<p>TODO</p>
<h3><a name="Footprint">Binary Footprint</a></h3>
<p>TODO</p>
<h2><a name="Wording">Proposed Wording</a></h2>
<h3>Header <code>&lt;format&gt;</code> synopsis</h3>
<pre>
<code>namespace std {
class format_error;
class format_args;
template &lt;class Char&gt;
basic_string&lt;Char&gt; format(const Char* fmt, format_args args);
template &lt;class Char, class ...Args&gt;
basic_string&lt;Char&gt; format(const Char* fmt, const Args&amp;... args);
}</code>
</pre>
<h3><a name="SyntaxRef">Format string syntax</a></h3>
<p>
Format strings contain <em>replacement fields</em> surrounded by curly braces
<code>{}</code>. Anything that is not contained in braces is considered literal
text, which is copied unchanged to the output. A brace character can be
included in the literal text by doubling: <code>{{</code> and <code>}}</code>.
</p>
<p>
The grammar for a replacement field is as follows:
</p>
<!-- The notation is the same as in n4296 22.4.3.1. -->
<pre>
<code>replacement-field ::= '{' [arg-id] [':' format-spec] '}'
arg-id ::= integer
integer ::= digit+
digit ::= '0'...'9'</code>
</pre>
<p>
In less formal terms, the replacement field can start with an
<code>arg-id</code> that specifies the argument whose value is to be formatted
and inserted into the output instead of the replacement field. The
<code>arg-id</code> is optionally followed by a <code>format-spec</code>,
which is preceded by a colon <code>':'</code>. These specify a non-default
format for the replacement value.
</p>
<p>
See also the <a href="FormatSpec">Format specification mini-language</a>
section.
</p>
<p>
If the numerical <code>arg-id</code>s 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.
</p>
<p>
Some simple format string examples:
</p>
<pre>
<code>"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}"</code>
</pre>
<p>
The <code>format-spec</code> 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 <em>formatting
mini-language</em> or interpretation of the <code>format-spec</code>.
</p>
<p>
Most built-in types support a common formatting mini-language, which is
described in the next section.
</p>
<p>
A <code>format-spec</code> field can also include nested replacement fields
in certain position within it. These nested replacement fields can contain only
an argument index; format specifications are not allowed. This allows the
formatting of a value to be dynamically specified.
</p>
<h4><a name="FormatSpec">Format specification mini-language</a></h4>
<p>
<em>Format specifications</em> are used within replacement fields contained
within a format string to define how individual values are presented (see
<a href="SyntaxRef">Format string syntax</a>). Each formattable type may define
how the format specification is to be interpreted.
</p>
<p>
Most built-in types implement the following options for format specifications,
although some of the formatting options are only supported by the numeric types.
</p>
<p>
The general form of a <em>standard format specifier</em> is:
</p>
<pre>
<code>format-spec ::= [[fill] align] [sign] ['#'] ['0'] [width] ['.' precision] [type]
fill ::= &lt;a character other than '{' or '}'&gt;
align ::= '<' | '>' | '=' | '^'
sign ::= '+' | '-' | ' '
width ::= integer | '{' arg-id '}'
precision ::= integer | '{' arg-id '}'
type ::= int-type | 'a' | 'A' | 'c' | 'e' | 'E' | 'f' | 'F' | 'g' | 'G' | 'p' | 's'
int-type ::= 'b' | 'B' | 'd' | 'o' | 'x' | 'X'</code>
</pre>
<p>
The <code>fill</code> character can be any character other than <code>'{'</code>
or <code>'}'</code>. 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 <code>format-spec</code> is not a valid alignment option,
then it is assumed that both the fill character and the alignment option are
absent.
<p>
The meaning of the various alignment options is as follows:
</p>
<table>
<thead>
<tr><th>Option</th><th>Meaning</th></tr>
</thead>
<tbody>
<tr>
<td><code>'&lt;'</code></td>
<td>Forces the field to be left-aligned within the available space (this is
the default for most objects).</td>
</tr>
<tr>
<td><code>'&gt;'</code></td>
<td>Forces the field to be right-aligned within the available space (this is
the default for numbers).</td>
</tr>
<tr>
<td><code>'='</code></td>
<td>Forces the padding to be placed after the sign (if any) but before the
digits. This is used for printing fields in the form
<code>+000000120</code>. This alignment option is only valid for numeric
types.</td>
</tr>
<tr>
<td><code>'^'</code></td>
<td>Forces the field to be centered within the available space.</td>
</tr>
</tbody>
</table>
<p>
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.
</p>
<p>
The <code>sign</code> option is only valid for number types, and can be one of
the following:
</p>
<table>
<thead>
<tr><th>Option</th><th>Meaning</th></tr>
</thead>
<tbody>
<tr>
<td><code>'+'</code></td>
<td>Indicates that a sign should be used for both positive as well as negative
numbers.</td>
</tr>
<tr>
<td><code>'-'</code></td>
<td>Indicates that a sign should be used only for negative numbers (this is
the default behavior).</td>
</tr>
<tr>
<td>space</td>
<td>Indicates that a leading space should be used on positive numbers, and a
minus sign on negative numbers.</td>
</tr>
</tbody>
</table>
<p>
The <code>'#'</code> option causes the <em>alternate form</em 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 <code>"0b"</code> (<code>"0B"</code>), <code>"0"</code>, or
<code>"0x"</code> (<code>"0X"</code>) 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 <code>"0x"</code> is used for the type <code>'x'</code>
and <code>"0X"</code> is used for <code>'X'</code>. 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 <code>'g'</code> and <code>'G'</code> conversions, trailing
zeros are not removed from the result.
</p>
<p>
<code>width</code> is a decimal integer defining the minimum field width. If
not specified, then the field width will be determined by the content.
</p>
<p>
Preceding the <code>width</code> field by a zero (<code>'0'</code>) character
enables sign-aware zero-padding for numeric types. This is equivalent to a
<code>fill</code> character of <code>'0'</code> with an <code>alignment</code>
type of <code>'='</code>.
</p>
<p>
The <code>precision</code> is a decimal number indicating how many digits should
be displayed after the decimal point for a floating-point value formatted with
<code>'f'</code> and <code>'F'</code>, or before and after the decimal point
for a floating-point value formatted with <code>'g'</code> or <code>'G'</code>.
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
<code>precision</code> is not allowed for integer, character, Boolean, and
pointer values.
</p>
<p>
Finally, the <code>type</code> determines how the data should be presented.
</p>
<p>The available string presentation types are:</p>
<table>
<thead>
<tr><th>Type</th><th>Meaning</th></tr>
</thead>
<tbody>
<tr>
<td><code>'s'</code></td>
<td>String format. This is the default type for strings and may be omitted.</td>
</tr>
<tr>
<td>none</td>
<td>The same as <code>'s'</code>.</td>
</tr>
</tbody>
</table>
<p>The available character presentation types are:</p>
<table>
<thead>
<tr><th>Type</th><th>Meaning</th></tr>
</thead>
<tbody>
<tr>
<td><code>'c'</code></td>
<td>Character format. This is the default type for characters and may be
omitted.</td>
</tr>
<tr>
<td>none</td>
<td>The same as <code>'c'</code>.</td>
</tr>
</tbody>
</table>
<p>The available integer presentation types are:</p>
<table>
<thead>
<tr><th>Type</th><th>Meaning</th></tr>
</thead>
<tbody>
<tr>
<td><code>'b'</code></td>
<td>Binary format. Outputs the number in base 2. Using the <code>'#'</code>
option with this type adds the prefix <code>"0b"</code> to the output
value.</td>
</tr>
<tr>
<td><code>'B'</code></td>
<td>Binary format. Outputs the number in base 2. Using the <code>'#'</code>
option with this type adds the prefix <code>"0B"</code> to the output
value.</td>
</tr>
<tr>
<td><code>'d'</code></td>
<td>Decimal integer. Outputs the number in base 10.</td>
</tr>
<tr>
<td><code>'o'</code></td>
<td>Octal format. Outputs the number in base 8.</td>
</tr>
<tr>
<td><code>'x'</code></td>
<td>Hex format. Outputs the number in base 16, using lower-case letters for the
digits above 9. Using the <code>'#'</code> option with this type adds the
prefix <code>"0x"</code> to the output value.</td>
</tr>
<tr>
<td><code>'X'</code></td>
<td>Hex format. Outputs the number in base 16, using upper-case letters for the
digits above 9. Using the <code>'#'</code> option with this type adds the
prefix <code>"0X"</code> to the output value.</td>
</tr>
<tr>
<td><code>'n'</code></td>
<td>Number. This is the same as <code>'d'</code>, except that it uses the
current locale setting to insert the appropriate number separator
characters.</td>
</tr>
<tr>
<td>none</td>
<td>The same as <code>'d'</code>.</td>
</tr>
</tbody>
</table>
<p>
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.
</p>
<p>The available presentation types for floating-point values are:</p>
<table>
<thead>
<tr><th>Type</th><th>Meaning</th></tr>
</thead>
<tbody>
<tr>
<td><code>'a'</code></td>
<td>Hexadecimal floating point format. Prints the number in base 16 with prefix
<code>"0x"</code> and lower-case letters for digits above 9. Uses
<code>'p'</code> to indicate the exponent.</td>
</tr>
<tr>
<td><code>'A'</code></td>
<td>Same as <code>'a'</code> except it uses upper-case letters for the prefix,
digits above 9 and to indicate the exponent.</td>
</tr>
<tr>
<td><code>'e'</code></td>
<td>Exponent notation. Prints the number in scientific notation using the
letter <code>'e'</code> to indicate the exponent.</td>
</tr>
<tr>
<td><code>'E'</code></td>
<td>Exponent notation. Same as <code>'e'</code> except it uses an upper-case
<code>'E'</code> as the separator character.</td>
</tr>
<tr>
<td><code>'f'</code></td>
<td>Fixed point. Displays the number as a fixed-point number.</td>
</tr>
<tr>
<td><code>'F'</code></td>
<td>Fixed point. Same as <code>'f'</code>, but converts <code>nan</code> to
<code>NAN</code> and <code>inf</code> to <code>INF</code>.</td>
</tr>
<tr>
<td><code>'g'</code></td>
<td>General format. For a given precision <code>p >= 1</code>, this rounds the
number to <code>p</code> significant digits and then formats the result in
either fixed-point format or in scientific notation, depending on its
magnitude.
A precision of <code>0</code> is treated as equivalent to a precision of
<code>1</code>.</td>
</tr>
<tr>
<td><code>'n'</code></td>
<td>Number. This is the same as <code>'g'</code>, except that it uses the
current locale setting to insert the appropriate number separator
characters.</td>
</tr>
<tr>
<td>none</td>
<td>The same as <code>'g'</code>.</td>
</tr>
</tbody>
</table>
<p>The available presentation types for pointers are:</p>
<table>
<thead>
<tr><th>Type</th><th>Meaning</th></tr>
</thead>
<tbody>
<tr>
<td><code>'p'</code></td>
<td>Pointer format. This is the default type for pointers and may be
omitted.</td>
</tr>
<tr>
<td>none</td>
<td>The same as <code>'p'</code>.</td>
</tr>
</tbody>
</table>
<h3>Class <code>format_error</code></h3>
<pre>
<code>class format_error : public std::runtime_error {
public:
explicit format_error(const string& what_arg);
explicit format_error(const char* what_arg);
};</code>
</pre>
<p>
The class <code>format_error</code> defines the type of objects thrown as
exceptions to report errors from the formatting library.
</p>
<dl>
<dt><code>format_error(const string& what_arg);</code></dt>
<dd>
<p><i>Effects</i>: Constructs an object of class <code>format_error</code>.</p>
<p><i>Postcondition</i>: <code>strcmp(what(), what_arg.c_str()) == 0</code>.</p>
</dd>
<dt><code>format_error(const char* what_arg);</code></dt>
<dd>
<p><i>Effects</i>: Constructs an object of class <code>format_error</code>.</p>
<p><i>Postcondition</i>: <code>strcmp(what(), what_arg) == 0</code>.</p>
</dd>
</dl>
<h3>Class <code>format_args</code></h3>
<p>TODO</p>
<h3>Function template <code>format</code></h3>
<dl>
<dt>
<code>template &lt;class Char&gt;<br>
&nbsp;&nbsp;basic_string&lt;Char&gt; format(const Char* fmt, format_args args);<br>
<br>
template &lt;class Char, class ...Args&gt;<br>
&nbsp;&nbsp;basic_string&lt;Char&gt; format(const Char* fmt, const Args&amp;... args);</code>
</dt>
<dd>
<p><i>Requires</i>: <code>fmt</code> shall not be a null pointer.</p>
<p>
<i>Effects</i>: Each function returns a <code>basic_string</code> object
constructed from the format string argument <code>fmt</code> with each
replacement field substituted with the character representation of the
argument it refers to, formatted according to the specification given in the
field.
</p>
<p><i>Returns</i>: The formatted string.</p>
<p><i>Throws</i>: <code>format_error</code> if <code>fmt</code> is not a valid
format string.</p>
</dd>
</dl>
<h2><a name="Implementation">Implementation</a></h2>
<p>
The ideas proposed in this paper have been implemented in the open-source fmt
library. TODO: link and mention other implementations (Boost Format, FastFormat)
</p>
<h2><a name="References">References</a></h2>
<p>
<a name="1">[1]</a>
<cite>The <code>fprintf</code> function. ISO/IEC 9899:2011. 7.21.6.1.</cite><br>
<a name="2">[2]</a>
<cite><a href="http://pubs.opengroup.org/onlinepubs/009695399/functions/fprintf.html">
fprintf, printf, snprintf, sprintf - print formatted output</a>. The Open
Group Base Specifications Issue 6 IEEE Std 1003.1, 2004 Edition.</cite><br>
<a name="3">[3]</a>
<cite><a href="https://docs.python.org/3/library/string.html#format-string-syntax">
6.1.3. Format String Syntax</a>. Python 3.5.2 documentation.</cite><br>
<a name="4">[4]</a>
<cite><a href="https://msdn.microsoft.com/en-us/library/system.string.format(v=vs.110).aspx">
String.Format Method</a>. .NET Framework Class Library.</cite><br>
<a name="5">[5]</a>
<cite><a href="https://doc.rust-lang.org/std/fmt/">
Module <code>std::fmt</code></a>. The Rust Standard Library.</cite><br>
<a name="6">[6]</a>
<cite><a href="https://msdn.microsoft.com/en-us/library/56e442dc(v=vs.120).aspx">
Format Specification Syntax: printf and wprintf Functions</a>. C++ Language and
Standard Libraries.</cite><br>
<a name="7">[7]</a>
<cite><a href="ftp://ftp.gnu.org/old-gnu/Manuals/gawk-3.1.0/html_chapter/gawk_11.html">
10.4.2 Rearranging printf Arguments</a>. The GNU Awk User's Guide.</cite><br>
</p>
</body>