comparison dep/fmt/doc/html/syntax.html @ 343:1faa72660932

*: transfer back to cmake from autotools autotools just made lots of things more complicated than they should have and many things broke (i.e. translations)
author Paper <paper@paper.us.eu.org>
date Thu, 20 Jun 2024 05:56:06 -0400
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131 <section id="format-string-syntax">
132 <span id="syntax"></span><h1>Format String Syntax<a class="headerlink" href="#format-string-syntax" title="Permalink to this headline">¶</a></h1>
133 <p>Formatting functions such as <a class="reference internal" href="api.html#format"><span class="std std-ref">fmt::format()</span></a> and
134 <a class="reference internal" href="api.html#print"><span class="std std-ref">fmt::print()</span></a> use the same format string syntax described in this
135 section.</p>
136 <p>Format strings contain “replacement fields” surrounded by curly braces <code class="docutils literal notranslate"><span class="pre">{}</span></code>.
137 Anything that is not contained in braces is considered literal text, which is
138 copied unchanged to the output. If you need to include a brace character in the
139 literal text, it can be escaped by doubling: <code class="docutils literal notranslate"><span class="pre">{{</span></code> and <code class="docutils literal notranslate"><span class="pre">}}</span></code>.</p>
140 <p>The grammar for a replacement field is as follows:</p>
141 <pre>
142 <strong id="grammar-token-sf-replacement_field"><span id="grammar-token-replacement-field"></span>replacement_field</strong> ::= &quot;{&quot; [<a class="reference internal" href="#grammar-token-sf-arg_id"><code class="xref docutils literal notranslate"><span class="pre">arg_id</span></code></a>] [&quot;:&quot; (<a class="reference internal" href="#grammar-token-sf-format_spec"><code class="xref docutils literal notranslate"><span class="pre">format_spec</span></code></a> | <a class="reference internal" href="#grammar-token-sf-chrono_format_spec"><code class="xref docutils literal notranslate"><span class="pre">chrono_format_spec</span></code></a>)] &quot;}&quot;
143 <strong id="grammar-token-sf-arg_id"><span id="grammar-token-arg-id"></span>arg_id </strong> ::= <a class="reference internal" href="#grammar-token-sf-integer"><code class="xref docutils literal notranslate"><span class="pre">integer</span></code></a> | <a class="reference internal" href="#grammar-token-sf-identifier"><code class="xref docutils literal notranslate"><span class="pre">identifier</span></code></a>
144 <strong id="grammar-token-sf-integer"><span id="grammar-token-integer"></span>integer </strong> ::= <a class="reference internal" href="#grammar-token-sf-digit"><code class="xref docutils literal notranslate"><span class="pre">digit</span></code></a>+
145 <strong id="grammar-token-sf-digit"><span id="grammar-token-digit"></span>digit </strong> ::= &quot;0&quot;...&quot;9&quot;
146 <strong id="grammar-token-sf-identifier"><span id="grammar-token-identifier"></span>identifier </strong> ::= <a class="reference internal" href="#grammar-token-sf-id_start"><code class="xref docutils literal notranslate"><span class="pre">id_start</span></code></a> <a class="reference internal" href="#grammar-token-sf-id_continue"><code class="xref docutils literal notranslate"><span class="pre">id_continue</span></code></a>*
147 <strong id="grammar-token-sf-id_start"><span id="grammar-token-id-start"></span>id_start </strong> ::= &quot;a&quot;...&quot;z&quot; | &quot;A&quot;...&quot;Z&quot; | &quot;_&quot;
148 <strong id="grammar-token-sf-id_continue"><span id="grammar-token-id-continue"></span>id_continue </strong> ::= <a class="reference internal" href="#grammar-token-sf-id_start"><code class="xref docutils literal notranslate"><span class="pre">id_start</span></code></a> | <a class="reference internal" href="#grammar-token-sf-digit"><code class="xref docutils literal notranslate"><span class="pre">digit</span></code></a>
149 </pre>
150 <p>In less formal terms, the replacement field can start with an <em>arg_id</em>
151 that specifies the argument whose value is to be formatted and inserted into
152 the output instead of the replacement field.
153 The <em>arg_id</em> is optionally followed by a <em>format_spec</em>, which is preceded by a
154 colon <code class="docutils literal notranslate"><span class="pre">':'</span></code>. These specify a non-default format for the replacement value.</p>
155 <p>See also the <a class="reference internal" href="#formatspec"><span class="std std-ref">Format Specification Mini-Language</span></a> section.</p>
156 <p>If the numerical arg_ids in a format string are 0, 1, 2, … in sequence,
157 they can all be omitted (not just some) and the numbers 0, 1, 2, … will be
158 automatically inserted in that order.</p>
159 <p>Named arguments can be referred to by their names or indices.</p>
160 <p>Some simple format string examples:</p>
161 <div class="highlight-c++ notranslate"><div class="highlight"><pre><span></span><span class="s">&quot;First, thou shalt count to {0}&quot;</span><span class="w"> </span><span class="c1">// References the first argument</span>
162 <span class="s">&quot;Bring me a {}&quot;</span><span class="w"> </span><span class="c1">// Implicitly references the first argument</span>
163 <span class="s">&quot;From {} to {}&quot;</span><span class="w"> </span><span class="c1">// Same as &quot;From {0} to {1}&quot;</span>
164 </pre></div>
165 </div>
166 <p>The <em>format_spec</em> field contains a specification of how the value should be
167 presented, including such details as field width, alignment, padding, decimal
168 precision and so on. Each value type can define its own “formatting
169 mini-language” or interpretation of the <em>format_spec</em>.</p>
170 <p>Most built-in types support a common formatting mini-language, which is
171 described in the next section.</p>
172 <p>A <em>format_spec</em> field can also include nested replacement fields in certain
173 positions within it. These nested replacement fields can contain only an
174 argument id; format specifications are not allowed. This allows the formatting
175 of a value to be dynamically specified.</p>
176 <p>See the <a class="reference internal" href="#formatexamples"><span class="std std-ref">Format Examples</span></a> section for some examples.</p>
177 <section id="format-specification-mini-language">
178 <span id="formatspec"></span><h2>Format Specification Mini-Language<a class="headerlink" href="#format-specification-mini-language" title="Permalink to this headline">¶</a></h2>
179 <p>“Format specifications” are used within replacement fields contained within a
180 format string to define how individual values are presented (see
181 <a class="reference internal" href="#syntax"><span class="std std-ref">Format String Syntax</span></a>). Each formattable type may define how the format
182 specification is to be interpreted.</p>
183 <p>Most built-in types implement the following options for format specifications,
184 although some of the formatting options are only supported by the numeric types.</p>
185 <p>The general form of a <em>standard format specifier</em> is:</p>
186 <pre>
187 <strong id="grammar-token-sf-format_spec"><span id="grammar-token-format-spec"></span>format_spec</strong> ::= [[<a class="reference internal" href="#grammar-token-sf-fill"><code class="xref docutils literal notranslate"><span class="pre">fill</span></code></a>]<a class="reference internal" href="#grammar-token-sf-align"><code class="xref docutils literal notranslate"><span class="pre">align</span></code></a>][<a class="reference internal" href="#grammar-token-sf-sign"><code class="xref docutils literal notranslate"><span class="pre">sign</span></code></a>][&quot;#&quot;][&quot;0&quot;][<a class="reference internal" href="#grammar-token-sf-width"><code class="xref docutils literal notranslate"><span class="pre">width</span></code></a>][&quot;.&quot; <a class="reference internal" href="#grammar-token-sf-precision"><code class="xref docutils literal notranslate"><span class="pre">precision</span></code></a>][&quot;L&quot;][<a class="reference internal" href="#grammar-token-sf-type"><code class="xref docutils literal notranslate"><span class="pre">type</span></code></a>]
188 <strong id="grammar-token-sf-fill"><span id="grammar-token-fill"></span>fill </strong> ::= &lt;a character other than '{' or '}'&gt;
189 <strong id="grammar-token-sf-align"><span id="grammar-token-align"></span>align </strong> ::= &quot;&lt;&quot; | &quot;&gt;&quot; | &quot;^&quot;
190 <strong id="grammar-token-sf-sign"><span id="grammar-token-sign"></span>sign </strong> ::= &quot;+&quot; | &quot;-&quot; | &quot; &quot;
191 <strong id="grammar-token-sf-width"><span id="grammar-token-width"></span>width </strong> ::= <a class="reference internal" href="#grammar-token-sf-integer"><code class="xref docutils literal notranslate"><span class="pre">integer</span></code></a> | &quot;{&quot; [<a class="reference internal" href="#grammar-token-sf-arg_id"><code class="xref docutils literal notranslate"><span class="pre">arg_id</span></code></a>] &quot;}&quot;
192 <strong id="grammar-token-sf-precision"><span id="grammar-token-precision"></span>precision </strong> ::= <a class="reference internal" href="#grammar-token-sf-integer"><code class="xref docutils literal notranslate"><span class="pre">integer</span></code></a> | &quot;{&quot; [<a class="reference internal" href="#grammar-token-sf-arg_id"><code class="xref docutils literal notranslate"><span class="pre">arg_id</span></code></a>] &quot;}&quot;
193 <strong id="grammar-token-sf-type"><span id="grammar-token-type"></span>type </strong> ::= &quot;a&quot; | &quot;A&quot; | &quot;b&quot; | &quot;B&quot; | &quot;c&quot; | &quot;d&quot; | &quot;e&quot; | &quot;E&quot; | &quot;f&quot; | &quot;F&quot; | &quot;g&quot; | &quot;G&quot; |
194 &quot;o&quot; | &quot;p&quot; | &quot;s&quot; | &quot;x&quot; | &quot;X&quot; | &quot;?&quot;
195 </pre>
196 <p>The <em>fill</em> character can be any Unicode code point other than <code class="docutils literal notranslate"><span class="pre">'{'</span></code> or
197 <code class="docutils literal notranslate"><span class="pre">'}'</span></code>. The presence of a fill character is signaled by the character following
198 it, which must be one of the alignment options. If the second character of
199 <em>format_spec</em> is not a valid alignment option, then it is assumed that both the
200 fill character and the alignment option are absent.</p>
201 <p>The meaning of the various alignment options is as follows:</p>
202 <table class="docutils align-default">
203 <colgroup>
204 <col style="width: 13%" />
205 <col style="width: 87%" />
206 </colgroup>
207 <thead>
208 <tr class="row-odd"><th class="head"><p>Option</p></th>
209 <th class="head"><p>Meaning</p></th>
210 </tr>
211 </thead>
212 <tbody>
213 <tr class="row-even"><td><p><code class="docutils literal notranslate"><span class="pre">'&lt;'</span></code></p></td>
214 <td><p>Forces the field to be left-aligned within the available
215 space (this is the default for most objects).</p></td>
216 </tr>
217 <tr class="row-odd"><td><p><code class="docutils literal notranslate"><span class="pre">'&gt;'</span></code></p></td>
218 <td><p>Forces the field to be right-aligned within the
219 available space (this is the default for numbers).</p></td>
220 </tr>
221 <tr class="row-even"><td><p><code class="docutils literal notranslate"><span class="pre">'^'</span></code></p></td>
222 <td><p>Forces the field to be centered within the available
223 space.</p></td>
224 </tr>
225 </tbody>
226 </table>
227 <p>Note that unless a minimum field width is defined, the field width will always
228 be the same size as the data to fill it, so that the alignment option has no
229 meaning in this case.</p>
230 <p>The <em>sign</em> option is only valid for floating point and signed integer types,
231 and can be one of the following:</p>
232 <table class="docutils align-default">
233 <colgroup>
234 <col style="width: 13%" />
235 <col style="width: 87%" />
236 </colgroup>
237 <thead>
238 <tr class="row-odd"><th class="head"><p>Option</p></th>
239 <th class="head"><p>Meaning</p></th>
240 </tr>
241 </thead>
242 <tbody>
243 <tr class="row-even"><td><p><code class="docutils literal notranslate"><span class="pre">'+'</span></code></p></td>
244 <td><p>indicates that a sign should be used for both
245 nonnegative as well as negative numbers.</p></td>
246 </tr>
247 <tr class="row-odd"><td><p><code class="docutils literal notranslate"><span class="pre">'-'</span></code></p></td>
248 <td><p>indicates that a sign should be used only for negative
249 numbers (this is the default behavior).</p></td>
250 </tr>
251 <tr class="row-even"><td><p>space</p></td>
252 <td><p>indicates that a leading space should be used on
253 nonnegative numbers, and a minus sign on negative numbers.</p></td>
254 </tr>
255 </tbody>
256 </table>
257 <p>The <code class="docutils literal notranslate"><span class="pre">'#'</span></code> option causes the “alternate form” to be used for the
258 conversion. The alternate form is defined differently for different
259 types. This option is only valid for integer and floating-point types.
260 For integers, when binary, octal, or hexadecimal output is used, this
261 option adds the prefix respective <code class="docutils literal notranslate"><span class="pre">&quot;0b&quot;</span></code> (<code class="docutils literal notranslate"><span class="pre">&quot;0B&quot;</span></code>), <code class="docutils literal notranslate"><span class="pre">&quot;0&quot;</span></code>, or
262 <code class="docutils literal notranslate"><span class="pre">&quot;0x&quot;</span></code> (<code class="docutils literal notranslate"><span class="pre">&quot;0X&quot;</span></code>) to the output value. Whether the prefix is
263 lower-case or upper-case is determined by the case of the type
264 specifier, for example, the prefix <code class="docutils literal notranslate"><span class="pre">&quot;0x&quot;</span></code> is used for the type <code class="docutils literal notranslate"><span class="pre">'x'</span></code>
265 and <code class="docutils literal notranslate"><span class="pre">&quot;0X&quot;</span></code> is used for <code class="docutils literal notranslate"><span class="pre">'X'</span></code>. For floating-point numbers the
266 alternate form causes the result of the conversion to always contain a
267 decimal-point character, even if no digits follow it. Normally, a
268 decimal-point character appears in the result of these conversions
269 only if a digit follows it. In addition, for <code class="docutils literal notranslate"><span class="pre">'g'</span></code> and <code class="docutils literal notranslate"><span class="pre">'G'</span></code>
270 conversions, trailing zeros are not removed from the result.</p>
271 <p><em>width</em> is a decimal integer defining the minimum field width. If not
272 specified, then the field width will be determined by the content.</p>
273 <p>Preceding the <em>width</em> field by a zero (<code class="docutils literal notranslate"><span class="pre">'0'</span></code>) character enables sign-aware
274 zero-padding for numeric types. It forces the padding to be placed after the
275 sign or base (if any) but before the digits. This is used for printing fields in
276 the form ‘+000000120’. This option is only valid for numeric types and it has no
277 effect on formatting of infinity and NaN.</p>
278 <p>The <em>precision</em> is a decimal number indicating how many digits should be
279 displayed after the decimal point for a floating-point value formatted with
280 <code class="docutils literal notranslate"><span class="pre">'f'</span></code> and <code class="docutils literal notranslate"><span class="pre">'F'</span></code>, or before and after the decimal point for a floating-point
281 value formatted with <code class="docutils literal notranslate"><span class="pre">'g'</span></code> or <code class="docutils literal notranslate"><span class="pre">'G'</span></code>. For non-number types the field
282 indicates the maximum field size - in other words, how many characters will be
283 used from the field content. The <em>precision</em> is not allowed for integer,
284 character, Boolean, and pointer values. Note that a C string must be
285 null-terminated even if precision is specified.</p>
286 <p>The <code class="docutils literal notranslate"><span class="pre">'L'</span></code> option uses the current locale setting to insert the appropriate
287 number separator characters. This option is only valid for numeric types.</p>
288 <p>Finally, the <em>type</em> determines how the data should be presented.</p>
289 <p>The available string presentation types are:</p>
290 <table class="docutils align-default">
291 <colgroup>
292 <col style="width: 13%" />
293 <col style="width: 87%" />
294 </colgroup>
295 <thead>
296 <tr class="row-odd"><th class="head"><p>Type</p></th>
297 <th class="head"><p>Meaning</p></th>
298 </tr>
299 </thead>
300 <tbody>
301 <tr class="row-even"><td><p><code class="docutils literal notranslate"><span class="pre">'s'</span></code></p></td>
302 <td><p>String format. This is the default type for strings and
303 may be omitted.</p></td>
304 </tr>
305 <tr class="row-odd"><td><p><code class="docutils literal notranslate"><span class="pre">'?'</span></code></p></td>
306 <td><p>Debug format. The string is quoted and special
307 characters escaped.</p></td>
308 </tr>
309 <tr class="row-even"><td><p>none</p></td>
310 <td><p>The same as <code class="docutils literal notranslate"><span class="pre">'s'</span></code>.</p></td>
311 </tr>
312 </tbody>
313 </table>
314 <p>The available character presentation types are:</p>
315 <table class="docutils align-default">
316 <colgroup>
317 <col style="width: 13%" />
318 <col style="width: 87%" />
319 </colgroup>
320 <thead>
321 <tr class="row-odd"><th class="head"><p>Type</p></th>
322 <th class="head"><p>Meaning</p></th>
323 </tr>
324 </thead>
325 <tbody>
326 <tr class="row-even"><td><p><code class="docutils literal notranslate"><span class="pre">'c'</span></code></p></td>
327 <td><p>Character format. This is the default type for
328 characters and may be omitted.</p></td>
329 </tr>
330 <tr class="row-odd"><td><p><code class="docutils literal notranslate"><span class="pre">'?'</span></code></p></td>
331 <td><p>Debug format. The character is quoted and special
332 characters escaped.</p></td>
333 </tr>
334 <tr class="row-even"><td><p>none</p></td>
335 <td><p>The same as <code class="docutils literal notranslate"><span class="pre">'c'</span></code>.</p></td>
336 </tr>
337 </tbody>
338 </table>
339 <p>The available integer presentation types are:</p>
340 <table class="docutils align-default">
341 <colgroup>
342 <col style="width: 13%" />
343 <col style="width: 87%" />
344 </colgroup>
345 <thead>
346 <tr class="row-odd"><th class="head"><p>Type</p></th>
347 <th class="head"><p>Meaning</p></th>
348 </tr>
349 </thead>
350 <tbody>
351 <tr class="row-even"><td><p><code class="docutils literal notranslate"><span class="pre">'b'</span></code></p></td>
352 <td><p>Binary format. Outputs the number in base 2. Using the
353 <code class="docutils literal notranslate"><span class="pre">'#'</span></code> option with this type adds the prefix <code class="docutils literal notranslate"><span class="pre">&quot;0b&quot;</span></code>
354 to the output value.</p></td>
355 </tr>
356 <tr class="row-odd"><td><p><code class="docutils literal notranslate"><span class="pre">'B'</span></code></p></td>
357 <td><p>Binary format. Outputs the number in base 2. Using the
358 <code class="docutils literal notranslate"><span class="pre">'#'</span></code> option with this type adds the prefix <code class="docutils literal notranslate"><span class="pre">&quot;0B&quot;</span></code>
359 to the output value.</p></td>
360 </tr>
361 <tr class="row-even"><td><p><code class="docutils literal notranslate"><span class="pre">'c'</span></code></p></td>
362 <td><p>Character format. Outputs the number as a character.</p></td>
363 </tr>
364 <tr class="row-odd"><td><p><code class="docutils literal notranslate"><span class="pre">'d'</span></code></p></td>
365 <td><p>Decimal integer. Outputs the number in base 10.</p></td>
366 </tr>
367 <tr class="row-even"><td><p><code class="docutils literal notranslate"><span class="pre">'o'</span></code></p></td>
368 <td><p>Octal format. Outputs the number in base 8.</p></td>
369 </tr>
370 <tr class="row-odd"><td><p><code class="docutils literal notranslate"><span class="pre">'x'</span></code></p></td>
371 <td><p>Hex format. Outputs the number in base 16, using
372 lower-case letters for the digits above 9. Using the
373 <code class="docutils literal notranslate"><span class="pre">'#'</span></code> option with this type adds the prefix <code class="docutils literal notranslate"><span class="pre">&quot;0x&quot;</span></code>
374 to the output value.</p></td>
375 </tr>
376 <tr class="row-even"><td><p><code class="docutils literal notranslate"><span class="pre">'X'</span></code></p></td>
377 <td><p>Hex format. Outputs the number in base 16, using
378 upper-case letters for the digits above 9. Using the
379 <code class="docutils literal notranslate"><span class="pre">'#'</span></code> option with this type adds the prefix <code class="docutils literal notranslate"><span class="pre">&quot;0X&quot;</span></code>
380 to the output value.</p></td>
381 </tr>
382 <tr class="row-odd"><td><p>none</p></td>
383 <td><p>The same as <code class="docutils literal notranslate"><span class="pre">'d'</span></code>.</p></td>
384 </tr>
385 </tbody>
386 </table>
387 <p>Integer presentation types can also be used with character and Boolean values
388 with the only exception that <code class="docutils literal notranslate"><span class="pre">'c'</span></code> cannot be used with <code class="xref cpp cpp-any docutils literal notranslate"><span class="pre">bool</span></code>. Boolean values
389 are formatted using textual representation, either <code class="docutils literal notranslate"><span class="pre">true</span></code> or <code class="docutils literal notranslate"><span class="pre">false</span></code>, if the
390 presentation type is not specified.</p>
391 <p>The available presentation types for floating-point values are:</p>
392 <table class="docutils align-default">
393 <colgroup>
394 <col style="width: 13%" />
395 <col style="width: 87%" />
396 </colgroup>
397 <thead>
398 <tr class="row-odd"><th class="head"><p>Type</p></th>
399 <th class="head"><p>Meaning</p></th>
400 </tr>
401 </thead>
402 <tbody>
403 <tr class="row-even"><td><p><code class="docutils literal notranslate"><span class="pre">'a'</span></code></p></td>
404 <td><p>Hexadecimal floating point format. Prints the number in
405 base 16 with prefix <code class="docutils literal notranslate"><span class="pre">&quot;0x&quot;</span></code> and lower-case letters for
406 digits above 9. Uses <code class="docutils literal notranslate"><span class="pre">'p'</span></code> to indicate the exponent.</p></td>
407 </tr>
408 <tr class="row-odd"><td><p><code class="docutils literal notranslate"><span class="pre">'A'</span></code></p></td>
409 <td><p>Same as <code class="docutils literal notranslate"><span class="pre">'a'</span></code> except it uses upper-case letters for
410 the prefix, digits above 9 and to indicate the exponent.</p></td>
411 </tr>
412 <tr class="row-even"><td><p><code class="docutils literal notranslate"><span class="pre">'e'</span></code></p></td>
413 <td><p>Exponent notation. Prints the number in scientific
414 notation using the letter ‘e’ to indicate the exponent.</p></td>
415 </tr>
416 <tr class="row-odd"><td><p><code class="docutils literal notranslate"><span class="pre">'E'</span></code></p></td>
417 <td><p>Exponent notation. Same as <code class="docutils literal notranslate"><span class="pre">'e'</span></code> except it uses an
418 upper-case <code class="docutils literal notranslate"><span class="pre">'E'</span></code> as the separator character.</p></td>
419 </tr>
420 <tr class="row-even"><td><p><code class="docutils literal notranslate"><span class="pre">'f'</span></code></p></td>
421 <td><p>Fixed point. Displays the number as a fixed-point
422 number.</p></td>
423 </tr>
424 <tr class="row-odd"><td><p><code class="docutils literal notranslate"><span class="pre">'F'</span></code></p></td>
425 <td><p>Fixed point. Same as <code class="docutils literal notranslate"><span class="pre">'f'</span></code>, but converts <code class="docutils literal notranslate"><span class="pre">nan</span></code> to
426 <code class="docutils literal notranslate"><span class="pre">NAN</span></code> and <code class="docutils literal notranslate"><span class="pre">inf</span></code> to <code class="docutils literal notranslate"><span class="pre">INF</span></code>.</p></td>
427 </tr>
428 <tr class="row-even"><td><p><code class="docutils literal notranslate"><span class="pre">'g'</span></code></p></td>
429 <td><p>General format. For a given precision <code class="docutils literal notranslate"><span class="pre">p</span> <span class="pre">&gt;=</span> <span class="pre">1</span></code>,
430 this rounds the number to <code class="docutils literal notranslate"><span class="pre">p</span></code> significant digits and
431 then formats the result in either fixed-point format
432 or in scientific notation, depending on its magnitude.</p>
433 <p>A precision of <code class="docutils literal notranslate"><span class="pre">0</span></code> is treated as equivalent to a
434 precision of <code class="docutils literal notranslate"><span class="pre">1</span></code>.</p>
435 </td>
436 </tr>
437 <tr class="row-odd"><td><p><code class="docutils literal notranslate"><span class="pre">'G'</span></code></p></td>
438 <td><p>General format. Same as <code class="docutils literal notranslate"><span class="pre">'g'</span></code> except switches to
439 <code class="docutils literal notranslate"><span class="pre">'E'</span></code> if the number gets too large. The
440 representations of infinity and NaN are uppercased, too.</p></td>
441 </tr>
442 <tr class="row-even"><td><p>none</p></td>
443 <td><p>Similar to <code class="docutils literal notranslate"><span class="pre">'g'</span></code>, except that the default precision is
444 as high as needed to represent the particular value.</p></td>
445 </tr>
446 </tbody>
447 </table>
448 <p>The available presentation types for pointers are:</p>
449 <table class="docutils align-default">
450 <colgroup>
451 <col style="width: 13%" />
452 <col style="width: 87%" />
453 </colgroup>
454 <thead>
455 <tr class="row-odd"><th class="head"><p>Type</p></th>
456 <th class="head"><p>Meaning</p></th>
457 </tr>
458 </thead>
459 <tbody>
460 <tr class="row-even"><td><p><code class="docutils literal notranslate"><span class="pre">'p'</span></code></p></td>
461 <td><p>Pointer format. This is the default type for
462 pointers and may be omitted.</p></td>
463 </tr>
464 <tr class="row-odd"><td><p>none</p></td>
465 <td><p>The same as <code class="docutils literal notranslate"><span class="pre">'p'</span></code>.</p></td>
466 </tr>
467 </tbody>
468 </table>
469 </section>
470 <section id="chrono-format-specifications">
471 <span id="chrono-specs"></span><h2>Chrono Format Specifications<a class="headerlink" href="#chrono-format-specifications" title="Permalink to this headline">¶</a></h2>
472 <p>Format specifications for chrono duration and time point types as well as
473 <code class="docutils literal notranslate"><span class="pre">std::tm</span></code> have the following syntax:</p>
474 <pre>
475 <strong id="grammar-token-sf-chrono_format_spec"><span id="grammar-token-chrono-format-spec"></span>chrono_format_spec</strong> ::= [[<a class="reference internal" href="#grammar-token-sf-fill"><code class="xref docutils literal notranslate"><span class="pre">fill</span></code></a>]<a class="reference internal" href="#grammar-token-sf-align"><code class="xref docutils literal notranslate"><span class="pre">align</span></code></a>][<a class="reference internal" href="#grammar-token-sf-width"><code class="xref docutils literal notranslate"><span class="pre">width</span></code></a>][&quot;.&quot; <a class="reference internal" href="#grammar-token-sf-precision"><code class="xref docutils literal notranslate"><span class="pre">precision</span></code></a>][<a class="reference internal" href="#grammar-token-sf-chrono_specs"><code class="xref docutils literal notranslate"><span class="pre">chrono_specs</span></code></a>]
476 <strong id="grammar-token-sf-chrono_specs"><span id="grammar-token-chrono-specs"></span>chrono_specs </strong> ::= [<a class="reference internal" href="#grammar-token-sf-chrono_specs"><code class="xref docutils literal notranslate"><span class="pre">chrono_specs</span></code></a>] <a class="reference internal" href="#grammar-token-sf-conversion_spec"><code class="xref docutils literal notranslate"><span class="pre">conversion_spec</span></code></a> | <a class="reference internal" href="#grammar-token-sf-chrono_specs"><code class="xref docutils literal notranslate"><span class="pre">chrono_specs</span></code></a> <a class="reference internal" href="#grammar-token-sf-literal_char"><code class="xref docutils literal notranslate"><span class="pre">literal_char</span></code></a>
477 <strong id="grammar-token-sf-conversion_spec"><span id="grammar-token-conversion-spec"></span>conversion_spec </strong> ::= &quot;%&quot; [<a class="reference internal" href="#grammar-token-sf-modifier"><code class="xref docutils literal notranslate"><span class="pre">modifier</span></code></a>] <a class="reference internal" href="#grammar-token-sf-chrono_type"><code class="xref docutils literal notranslate"><span class="pre">chrono_type</span></code></a>
478 <strong id="grammar-token-sf-literal_char"><span id="grammar-token-literal-char"></span>literal_char </strong> ::= &lt;a character other than '{', '}' or '%'&gt;
479 <strong id="grammar-token-sf-modifier"><span id="grammar-token-modifier"></span>modifier </strong> ::= &quot;E&quot; | &quot;O&quot;
480 <strong id="grammar-token-sf-chrono_type"><span id="grammar-token-chrono-type"></span>chrono_type </strong> ::= &quot;a&quot; | &quot;A&quot; | &quot;b&quot; | &quot;B&quot; | &quot;c&quot; | &quot;C&quot; | &quot;d&quot; | &quot;D&quot; | &quot;e&quot; | &quot;F&quot; |
481 &quot;g&quot; | &quot;G&quot; | &quot;h&quot; | &quot;H&quot; | &quot;I&quot; | &quot;j&quot; | &quot;m&quot; | &quot;M&quot; | &quot;n&quot; | &quot;p&quot; |
482 &quot;q&quot; | &quot;Q&quot; | &quot;r&quot; | &quot;R&quot; | &quot;S&quot; | &quot;t&quot; | &quot;T&quot; | &quot;u&quot; | &quot;U&quot; | &quot;V&quot; |
483 &quot;w&quot; | &quot;W&quot; | &quot;x&quot; | &quot;X&quot; | &quot;y&quot; | &quot;Y&quot; | &quot;z&quot; | &quot;Z&quot; | &quot;%&quot;
484 </pre>
485 <p>Literal chars are copied unchanged to the output. Precision is valid only for
486 <code class="docutils literal notranslate"><span class="pre">std::chrono::duration</span></code> types with a floating-point representation type.</p>
487 <p>The available presentation types (<em>chrono_type</em>) are:</p>
488 <table class="docutils align-default">
489 <colgroup>
490 <col style="width: 12%" />
491 <col style="width: 88%" />
492 </colgroup>
493 <thead>
494 <tr class="row-odd"><th class="head"><p>Type</p></th>
495 <th class="head"><p>Meaning</p></th>
496 </tr>
497 </thead>
498 <tbody>
499 <tr class="row-even"><td><p><code class="docutils literal notranslate"><span class="pre">'a'</span></code></p></td>
500 <td><p>The abbreviated weekday name, e.g. “Sat”. If the value does not
501 contain a valid weekday, an exception of type <code class="docutils literal notranslate"><span class="pre">format_error</span></code> is
502 thrown.</p></td>
503 </tr>
504 <tr class="row-odd"><td><p><code class="docutils literal notranslate"><span class="pre">'A'</span></code></p></td>
505 <td><p>The full weekday name, e.g. “Saturday”. If the value does not
506 contain a valid weekday, an exception of type <code class="docutils literal notranslate"><span class="pre">format_error</span></code> is
507 thrown.</p></td>
508 </tr>
509 <tr class="row-even"><td><p><code class="docutils literal notranslate"><span class="pre">'b'</span></code></p></td>
510 <td><p>The abbreviated month name, e.g. “Nov”. If the value does not
511 contain a valid month, an exception of type <code class="docutils literal notranslate"><span class="pre">format_error</span></code> is
512 thrown.</p></td>
513 </tr>
514 <tr class="row-odd"><td><p><code class="docutils literal notranslate"><span class="pre">'B'</span></code></p></td>
515 <td><p>The full month name, e.g. “November”. If the value does not
516 contain a valid month, an exception of type <code class="docutils literal notranslate"><span class="pre">format_error</span></code> is
517 thrown.</p></td>
518 </tr>
519 <tr class="row-even"><td><p><code class="docutils literal notranslate"><span class="pre">'c'</span></code></p></td>
520 <td><p>The date and time representation, e.g. “Sat Nov 12 22:04:00 1955”.
521 The modified command <code class="docutils literal notranslate"><span class="pre">%Ec</span></code> produces the locale’s alternate date
522 and time representation.</p></td>
523 </tr>
524 <tr class="row-odd"><td><p><code class="docutils literal notranslate"><span class="pre">'C'</span></code></p></td>
525 <td><p>The year divided by 100 using floored division, e.g. “55”. If the
526 result is a single decimal digit, it is prefixed with 0.
527 The modified command <code class="docutils literal notranslate"><span class="pre">%EC</span></code> produces the locale’s alternative
528 representation of the century.</p></td>
529 </tr>
530 <tr class="row-even"><td><p><code class="docutils literal notranslate"><span class="pre">'d'</span></code></p></td>
531 <td><p>The day of month as a decimal number. If the result is a single
532 decimal digit, it is prefixed with 0. The modified command <code class="docutils literal notranslate"><span class="pre">%Od</span></code>
533 produces the locale’s alternative representation.</p></td>
534 </tr>
535 <tr class="row-odd"><td><p><code class="docutils literal notranslate"><span class="pre">'D'</span></code></p></td>
536 <td><p>Equivalent to <code class="docutils literal notranslate"><span class="pre">%m/%d/%y</span></code>, e.g. “11/12/55”.</p></td>
537 </tr>
538 <tr class="row-even"><td><p><code class="docutils literal notranslate"><span class="pre">'e'</span></code></p></td>
539 <td><p>The day of month as a decimal number. If the result is a single
540 decimal digit, it is prefixed with a space. The modified command
541 <code class="docutils literal notranslate"><span class="pre">%Oe</span></code> produces the locale’s alternative representation.</p></td>
542 </tr>
543 <tr class="row-odd"><td><p><code class="docutils literal notranslate"><span class="pre">'F'</span></code></p></td>
544 <td><p>Equivalent to <code class="docutils literal notranslate"><span class="pre">%Y-%m-%d</span></code>, e.g. “1955-11-12”.</p></td>
545 </tr>
546 <tr class="row-even"><td><p><code class="docutils literal notranslate"><span class="pre">'g'</span></code></p></td>
547 <td><p>The last two decimal digits of the ISO week-based year. If the
548 result is a single digit it is prefixed by 0.</p></td>
549 </tr>
550 <tr class="row-odd"><td><p><code class="docutils literal notranslate"><span class="pre">'G'</span></code></p></td>
551 <td><p>The ISO week-based year as a decimal number. If the result is less
552 than four digits it is left-padded with 0 to four digits.</p></td>
553 </tr>
554 <tr class="row-even"><td><p><code class="docutils literal notranslate"><span class="pre">'h'</span></code></p></td>
555 <td><p>Equivalent to <code class="docutils literal notranslate"><span class="pre">%b</span></code>, e.g. “Nov”.</p></td>
556 </tr>
557 <tr class="row-odd"><td><p><code class="docutils literal notranslate"><span class="pre">'H'</span></code></p></td>
558 <td><p>The hour (24-hour clock) as a decimal number. If the result is a
559 single digit, it is prefixed with 0. The modified command <code class="docutils literal notranslate"><span class="pre">%OH</span></code>
560 produces the locale’s alternative representation.</p></td>
561 </tr>
562 <tr class="row-even"><td><p><code class="docutils literal notranslate"><span class="pre">'I'</span></code></p></td>
563 <td><p>The hour (12-hour clock) as a decimal number. If the result is a
564 single digit, it is prefixed with 0. The modified command <code class="docutils literal notranslate"><span class="pre">%OI</span></code>
565 produces the locale’s alternative representation.</p></td>
566 </tr>
567 <tr class="row-odd"><td><p><code class="docutils literal notranslate"><span class="pre">'j'</span></code></p></td>
568 <td><p>If the type being formatted is a specialization of duration, the
569 decimal number of days without padding. Otherwise, the day of the
570 year as a decimal number. Jan 1 is 001. If the result is less than
571 three digits, it is left-padded with 0 to three digits.</p></td>
572 </tr>
573 <tr class="row-even"><td><p><code class="docutils literal notranslate"><span class="pre">'m'</span></code></p></td>
574 <td><p>The month as a decimal number. Jan is 01. If the result is a
575 single digit, it is prefixed with 0. The modified command <code class="docutils literal notranslate"><span class="pre">%Om</span></code>
576 produces the locale’s alternative representation.</p></td>
577 </tr>
578 <tr class="row-odd"><td><p><code class="docutils literal notranslate"><span class="pre">'M'</span></code></p></td>
579 <td><p>The minute as a decimal number. If the result is a single digit,
580 it is prefixed with 0. The modified command <code class="docutils literal notranslate"><span class="pre">%OM</span></code> produces the
581 locale’s alternative representation.</p></td>
582 </tr>
583 <tr class="row-even"><td><p><code class="docutils literal notranslate"><span class="pre">'n'</span></code></p></td>
584 <td><p>A new-line character.</p></td>
585 </tr>
586 <tr class="row-odd"><td><p><code class="docutils literal notranslate"><span class="pre">'p'</span></code></p></td>
587 <td><p>The AM/PM designations associated with a 12-hour clock.</p></td>
588 </tr>
589 <tr class="row-even"><td><p><code class="docutils literal notranslate"><span class="pre">'q'</span></code></p></td>
590 <td><p>The duration’s unit suffix.</p></td>
591 </tr>
592 <tr class="row-odd"><td><p><code class="docutils literal notranslate"><span class="pre">'Q'</span></code></p></td>
593 <td><p>The duration’s numeric value (as if extracted via <code class="docutils literal notranslate"><span class="pre">.count()</span></code>).</p></td>
594 </tr>
595 <tr class="row-even"><td><p><code class="docutils literal notranslate"><span class="pre">'r'</span></code></p></td>
596 <td><p>The 12-hour clock time, e.g. “10:04:00 PM”.</p></td>
597 </tr>
598 <tr class="row-odd"><td><p><code class="docutils literal notranslate"><span class="pre">'R'</span></code></p></td>
599 <td><p>Equivalent to <code class="docutils literal notranslate"><span class="pre">%H:%M</span></code>, e.g. “22:04”.</p></td>
600 </tr>
601 <tr class="row-even"><td><p><code class="docutils literal notranslate"><span class="pre">'S'</span></code></p></td>
602 <td><p>Seconds as a decimal number. If the number of seconds is less than
603 10, the result is prefixed with 0. If the precision of the input
604 cannot be exactly represented with seconds, then the format is a
605 decimal floating-point number with a fixed format and a precision
606 matching that of the precision of the input (or to a microseconds
607 precision if the conversion to floating-point decimal seconds
608 cannot be made within 18 fractional digits). The character for the
609 decimal point is localized according to the locale. The modified
610 command <code class="docutils literal notranslate"><span class="pre">%OS</span></code> produces the locale’s alternative representation.</p></td>
611 </tr>
612 <tr class="row-odd"><td><p><code class="docutils literal notranslate"><span class="pre">'t'</span></code></p></td>
613 <td><p>A horizontal-tab character.</p></td>
614 </tr>
615 <tr class="row-even"><td><p><code class="docutils literal notranslate"><span class="pre">'T'</span></code></p></td>
616 <td><p>Equivalent to <code class="docutils literal notranslate"><span class="pre">%H:%M:%S</span></code>.</p></td>
617 </tr>
618 <tr class="row-odd"><td><p><code class="docutils literal notranslate"><span class="pre">'u'</span></code></p></td>
619 <td><p>The ISO weekday as a decimal number (1-7), where Monday is 1. The
620 modified command <code class="docutils literal notranslate"><span class="pre">%Ou</span></code> produces the locale’s alternative
621 representation.</p></td>
622 </tr>
623 <tr class="row-even"><td><p><code class="docutils literal notranslate"><span class="pre">'U'</span></code></p></td>
624 <td><p>The week number of the year as a decimal number. The first Sunday
625 of the year is the first day of week 01. Days of the same year
626 prior to that are in week 00. If the result is a single digit, it
627 is prefixed with 0. The modified command <code class="docutils literal notranslate"><span class="pre">%OU</span></code> produces the
628 locale’s alternative representation.</p></td>
629 </tr>
630 <tr class="row-odd"><td><p><code class="docutils literal notranslate"><span class="pre">'V'</span></code></p></td>
631 <td><p>The ISO week-based week number as a decimal number. If the result
632 is a single digit, it is prefixed with 0. The modified command
633 <code class="docutils literal notranslate"><span class="pre">%OV</span></code> produces the locale’s alternative representation.</p></td>
634 </tr>
635 <tr class="row-even"><td><p><code class="docutils literal notranslate"><span class="pre">'w'</span></code></p></td>
636 <td><p>The weekday as a decimal number (0-6), where Sunday is 0.
637 The modified command <code class="docutils literal notranslate"><span class="pre">%Ow</span></code> produces the locale’s alternative
638 representation.</p></td>
639 </tr>
640 <tr class="row-odd"><td><p><code class="docutils literal notranslate"><span class="pre">'W'</span></code></p></td>
641 <td><p>The week number of the year as a decimal number. The first Monday
642 of the year is the first day of week 01. Days of the same year
643 prior to that are in week 00. If the result is a single digit, it
644 is prefixed with 0. The modified command <code class="docutils literal notranslate"><span class="pre">%OW</span></code> produces the
645 locale’s alternative representation.</p></td>
646 </tr>
647 <tr class="row-even"><td><p><code class="docutils literal notranslate"><span class="pre">'x'</span></code></p></td>
648 <td><p>The date representation, e.g. “11/12/55”. The modified command
649 <code class="docutils literal notranslate"><span class="pre">%Ex</span></code> produces the locale’s alternate date representation.</p></td>
650 </tr>
651 <tr class="row-odd"><td><p><code class="docutils literal notranslate"><span class="pre">'X'</span></code></p></td>
652 <td><p>The time representation, e.g. “10:04:00”. The modified command
653 <code class="docutils literal notranslate"><span class="pre">%EX</span></code> produces the locale’s alternate time representation.</p></td>
654 </tr>
655 <tr class="row-even"><td><p><code class="docutils literal notranslate"><span class="pre">'y'</span></code></p></td>
656 <td><p>The last two decimal digits of the year. If the result is a single
657 digit it is prefixed by 0. The modified command <code class="docutils literal notranslate"><span class="pre">%Oy</span></code> produces
658 the locale’s alternative representation. The modified command
659 <code class="docutils literal notranslate"><span class="pre">%Ey</span></code> produces the locale’s alternative representation of offset
660 from <code class="docutils literal notranslate"><span class="pre">%EC</span></code> (year only).</p></td>
661 </tr>
662 <tr class="row-odd"><td><p><code class="docutils literal notranslate"><span class="pre">'Y'</span></code></p></td>
663 <td><p>The year as a decimal number. If the result is less than four
664 digits it is left-padded with 0 to four digits. The modified
665 command <code class="docutils literal notranslate"><span class="pre">%EY</span></code> produces the locale’s alternative full year
666 representation.</p></td>
667 </tr>
668 <tr class="row-even"><td><p><code class="docutils literal notranslate"><span class="pre">'z'</span></code></p></td>
669 <td><p>The offset from UTC in the ISO 8601:2004 format. For example -0430
670 refers to 4 hours 30 minutes behind UTC. If the offset is zero,
671 +0000 is used. The modified commands <code class="docutils literal notranslate"><span class="pre">%Ez</span></code> and <code class="docutils literal notranslate"><span class="pre">%Oz</span></code> insert a
672 <code class="docutils literal notranslate"><span class="pre">:</span></code> between the hours and minutes: -04:30. If the offset
673 information is not available, an exception of type
674 <code class="docutils literal notranslate"><span class="pre">format_error</span></code> is thrown.</p></td>
675 </tr>
676 <tr class="row-odd"><td><p><code class="docutils literal notranslate"><span class="pre">'Z'</span></code></p></td>
677 <td><p>The time zone abbreviation. If the time zone abbreviation is not
678 available, an exception of type <code class="docutils literal notranslate"><span class="pre">format_error</span></code> is thrown.</p></td>
679 </tr>
680 <tr class="row-even"><td><p><code class="docutils literal notranslate"><span class="pre">'%'</span></code></p></td>
681 <td><p>A % character.</p></td>
682 </tr>
683 </tbody>
684 </table>
685 <p>Specifiers that have a calendaric component such as <code class="docutils literal notranslate"><span class="pre">'d'</span></code> (the day of month)
686 are valid only for <code class="docutils literal notranslate"><span class="pre">std::tm</span></code> and time points but not durations.</p>
687 </section>
688 <section id="range-format-specifications">
689 <h2>Range Format Specifications<a class="headerlink" href="#range-format-specifications" title="Permalink to this headline">¶</a></h2>
690 <p>Format specifications for range types have the following syntax:</p>
691 <pre>
692 <strong id="grammar-token-sf-range_format_spec"><span id="grammar-token-range-format-spec"></span>range_format_spec</strong> ::= [&quot;:&quot; [<code class="xref docutils literal notranslate"><span class="pre">underlying_spec</span></code>]]
693 </pre>
694 <p>The <code class="xref cpp cpp-any docutils literal notranslate"><span class="pre">underlying_spec</span></code> is parsed based on the formatter of the range’s
695 reference type.</p>
696 <p>By default, a range of characters or strings is printed escaped and quoted. But
697 if any <code class="xref cpp cpp-any docutils literal notranslate"><span class="pre">underlying_spec</span></code> is provided (even if it is empty), then the characters
698 or strings are printed according to the provided specification.</p>
699 <p>Examples:</p>
700 <div class="highlight-c++ notranslate"><div class="highlight"><pre><span></span><span class="n">fmt</span><span class="o">::</span><span class="n">format</span><span class="p">(</span><span class="s">&quot;{}&quot;</span><span class="p">,</span><span class="w"> </span><span class="n">std</span><span class="o">::</span><span class="n">vector</span><span class="p">{</span><span class="mi">10</span><span class="p">,</span><span class="w"> </span><span class="mi">20</span><span class="p">,</span><span class="w"> </span><span class="mi">30</span><span class="p">});</span>
701 <span class="c1">// Result: [10, 20, 30]</span>
702 <span class="n">fmt</span><span class="o">::</span><span class="n">format</span><span class="p">(</span><span class="s">&quot;{::#x}&quot;</span><span class="p">,</span><span class="w"> </span><span class="n">std</span><span class="o">::</span><span class="n">vector</span><span class="p">{</span><span class="mi">10</span><span class="p">,</span><span class="w"> </span><span class="mi">20</span><span class="p">,</span><span class="w"> </span><span class="mi">30</span><span class="p">});</span>
703 <span class="c1">// Result: [0xa, 0x14, 0x1e]</span>
704 <span class="n">fmt</span><span class="o">::</span><span class="n">format</span><span class="p">(</span><span class="s">&quot;{}&quot;</span><span class="p">,</span><span class="w"> </span><span class="n">vector</span><span class="p">{</span><span class="sc">&#39;h&#39;</span><span class="p">,</span><span class="w"> </span><span class="sc">&#39;e&#39;</span><span class="p">,</span><span class="w"> </span><span class="sc">&#39;l&#39;</span><span class="p">,</span><span class="w"> </span><span class="sc">&#39;l&#39;</span><span class="p">,</span><span class="w"> </span><span class="sc">&#39;o&#39;</span><span class="p">});</span>
705 <span class="c1">// Result: [&#39;h&#39;, &#39;e&#39;, &#39;l&#39;, &#39;l&#39;, &#39;o&#39;]</span>
706 <span class="n">fmt</span><span class="o">::</span><span class="n">format</span><span class="p">(</span><span class="s">&quot;{::}&quot;</span><span class="p">,</span><span class="w"> </span><span class="n">vector</span><span class="p">{</span><span class="sc">&#39;h&#39;</span><span class="p">,</span><span class="w"> </span><span class="sc">&#39;e&#39;</span><span class="p">,</span><span class="w"> </span><span class="sc">&#39;l&#39;</span><span class="p">,</span><span class="w"> </span><span class="sc">&#39;l&#39;</span><span class="p">,</span><span class="w"> </span><span class="sc">&#39;o&#39;</span><span class="p">});</span>
707 <span class="c1">// Result: [h, e, l, l, o]</span>
708 <span class="n">fmt</span><span class="o">::</span><span class="n">format</span><span class="p">(</span><span class="s">&quot;{::d}&quot;</span><span class="p">,</span><span class="w"> </span><span class="n">vector</span><span class="p">{</span><span class="sc">&#39;h&#39;</span><span class="p">,</span><span class="w"> </span><span class="sc">&#39;e&#39;</span><span class="p">,</span><span class="w"> </span><span class="sc">&#39;l&#39;</span><span class="p">,</span><span class="w"> </span><span class="sc">&#39;l&#39;</span><span class="p">,</span><span class="w"> </span><span class="sc">&#39;o&#39;</span><span class="p">});</span>
709 <span class="c1">// Result: [104, 101, 108, 108, 111]</span>
710 </pre></div>
711 </div>
712 </section>
713 <section id="format-examples">
714 <span id="formatexamples"></span><h2>Format Examples<a class="headerlink" href="#format-examples" title="Permalink to this headline">¶</a></h2>
715 <p>This section contains examples of the format syntax and comparison with
716 the printf formatting.</p>
717 <p>In most of the cases the syntax is similar to the printf formatting, with the
718 addition of the <code class="docutils literal notranslate"><span class="pre">{}</span></code> and with <code class="docutils literal notranslate"><span class="pre">:</span></code> used instead of <code class="docutils literal notranslate"><span class="pre">%</span></code>.
719 For example, <code class="docutils literal notranslate"><span class="pre">&quot;%03.2f&quot;</span></code> can be translated to <code class="docutils literal notranslate"><span class="pre">&quot;{:03.2f}&quot;</span></code>.</p>
720 <p>The new format syntax also supports new and different options, shown in the
721 following examples.</p>
722 <p>Accessing arguments by position:</p>
723 <div class="highlight-c++ notranslate"><div class="highlight"><pre><span></span><span class="n">fmt</span><span class="o">::</span><span class="n">format</span><span class="p">(</span><span class="s">&quot;{0}, {1}, {2}&quot;</span><span class="p">,</span><span class="w"> </span><span class="sc">&#39;a&#39;</span><span class="p">,</span><span class="w"> </span><span class="sc">&#39;b&#39;</span><span class="p">,</span><span class="w"> </span><span class="sc">&#39;c&#39;</span><span class="p">);</span>
724 <span class="c1">// Result: &quot;a, b, c&quot;</span>
725 <span class="n">fmt</span><span class="o">::</span><span class="n">format</span><span class="p">(</span><span class="s">&quot;{}, {}, {}&quot;</span><span class="p">,</span><span class="w"> </span><span class="sc">&#39;a&#39;</span><span class="p">,</span><span class="w"> </span><span class="sc">&#39;b&#39;</span><span class="p">,</span><span class="w"> </span><span class="sc">&#39;c&#39;</span><span class="p">);</span>
726 <span class="c1">// Result: &quot;a, b, c&quot;</span>
727 <span class="n">fmt</span><span class="o">::</span><span class="n">format</span><span class="p">(</span><span class="s">&quot;{2}, {1}, {0}&quot;</span><span class="p">,</span><span class="w"> </span><span class="sc">&#39;a&#39;</span><span class="p">,</span><span class="w"> </span><span class="sc">&#39;b&#39;</span><span class="p">,</span><span class="w"> </span><span class="sc">&#39;c&#39;</span><span class="p">);</span>
728 <span class="c1">// Result: &quot;c, b, a&quot;</span>
729 <span class="n">fmt</span><span class="o">::</span><span class="n">format</span><span class="p">(</span><span class="s">&quot;{0}{1}{0}&quot;</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;abra&quot;</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;cad&quot;</span><span class="p">);</span><span class="w"> </span><span class="c1">// arguments&#39; indices can be repeated</span>
730 <span class="c1">// Result: &quot;abracadabra&quot;</span>
731 </pre></div>
732 </div>
733 <p>Aligning the text and specifying a width:</p>
734 <div class="highlight-c++ notranslate"><div class="highlight"><pre><span></span><span class="n">fmt</span><span class="o">::</span><span class="n">format</span><span class="p">(</span><span class="s">&quot;{:&lt;30}&quot;</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;left aligned&quot;</span><span class="p">);</span>
735 <span class="c1">// Result: &quot;left aligned &quot;</span>
736 <span class="n">fmt</span><span class="o">::</span><span class="n">format</span><span class="p">(</span><span class="s">&quot;{:&gt;30}&quot;</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;right aligned&quot;</span><span class="p">);</span>
737 <span class="c1">// Result: &quot; right aligned&quot;</span>
738 <span class="n">fmt</span><span class="o">::</span><span class="n">format</span><span class="p">(</span><span class="s">&quot;{:^30}&quot;</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;centered&quot;</span><span class="p">);</span>
739 <span class="c1">// Result: &quot; centered &quot;</span>
740 <span class="n">fmt</span><span class="o">::</span><span class="n">format</span><span class="p">(</span><span class="s">&quot;{:*^30}&quot;</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;centered&quot;</span><span class="p">);</span><span class="w"> </span><span class="c1">// use &#39;*&#39; as a fill char</span>
741 <span class="c1">// Result: &quot;***********centered***********&quot;</span>
742 </pre></div>
743 </div>
744 <p>Dynamic width:</p>
745 <div class="highlight-c++ notranslate"><div class="highlight"><pre><span></span><span class="n">fmt</span><span class="o">::</span><span class="n">format</span><span class="p">(</span><span class="s">&quot;{:&lt;{}}&quot;</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;left aligned&quot;</span><span class="p">,</span><span class="w"> </span><span class="mi">30</span><span class="p">);</span>
746 <span class="c1">// Result: &quot;left aligned &quot;</span>
747 </pre></div>
748 </div>
749 <p>Dynamic precision:</p>
750 <div class="highlight-c++ notranslate"><div class="highlight"><pre><span></span><span class="n">fmt</span><span class="o">::</span><span class="n">format</span><span class="p">(</span><span class="s">&quot;{:.{}f}&quot;</span><span class="p">,</span><span class="w"> </span><span class="mf">3.14</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="p">);</span>
751 <span class="c1">// Result: &quot;3.1&quot;</span>
752 </pre></div>
753 </div>
754 <p>Replacing <code class="docutils literal notranslate"><span class="pre">%+f</span></code>, <code class="docutils literal notranslate"><span class="pre">%-f</span></code>, and <code class="docutils literal notranslate"><span class="pre">%</span> <span class="pre">f</span></code> and specifying a sign:</p>
755 <div class="highlight-c++ notranslate"><div class="highlight"><pre><span></span><span class="n">fmt</span><span class="o">::</span><span class="n">format</span><span class="p">(</span><span class="s">&quot;{:+f}; {:+f}&quot;</span><span class="p">,</span><span class="w"> </span><span class="mf">3.14</span><span class="p">,</span><span class="w"> </span><span class="mf">-3.14</span><span class="p">);</span><span class="w"> </span><span class="c1">// show it always</span>
756 <span class="c1">// Result: &quot;+3.140000; -3.140000&quot;</span>
757 <span class="n">fmt</span><span class="o">::</span><span class="n">format</span><span class="p">(</span><span class="s">&quot;{: f}; {: f}&quot;</span><span class="p">,</span><span class="w"> </span><span class="mf">3.14</span><span class="p">,</span><span class="w"> </span><span class="mf">-3.14</span><span class="p">);</span><span class="w"> </span><span class="c1">// show a space for positive numbers</span>
758 <span class="c1">// Result: &quot; 3.140000; -3.140000&quot;</span>
759 <span class="n">fmt</span><span class="o">::</span><span class="n">format</span><span class="p">(</span><span class="s">&quot;{:-f}; {:-f}&quot;</span><span class="p">,</span><span class="w"> </span><span class="mf">3.14</span><span class="p">,</span><span class="w"> </span><span class="mf">-3.14</span><span class="p">);</span><span class="w"> </span><span class="c1">// show only the minus -- same as &#39;{:f}; {:f}&#39;</span>
760 <span class="c1">// Result: &quot;3.140000; -3.140000&quot;</span>
761 </pre></div>
762 </div>
763 <p>Replacing <code class="docutils literal notranslate"><span class="pre">%x</span></code> and <code class="docutils literal notranslate"><span class="pre">%o</span></code> and converting the value to different bases:</p>
764 <div class="highlight-c++ notranslate"><div class="highlight"><pre><span></span><span class="n">fmt</span><span class="o">::</span><span class="n">format</span><span class="p">(</span><span class="s">&quot;int: {0:d}; hex: {0:x}; oct: {0:o}; bin: {0:b}&quot;</span><span class="p">,</span><span class="w"> </span><span class="mi">42</span><span class="p">);</span>
765 <span class="c1">// Result: &quot;int: 42; hex: 2a; oct: 52; bin: 101010&quot;</span>
766 <span class="c1">// with 0x or 0 or 0b as prefix:</span>
767 <span class="n">fmt</span><span class="o">::</span><span class="n">format</span><span class="p">(</span><span class="s">&quot;int: {0:d}; hex: {0:#x}; oct: {0:#o}; bin: {0:#b}&quot;</span><span class="p">,</span><span class="w"> </span><span class="mi">42</span><span class="p">);</span>
768 <span class="c1">// Result: &quot;int: 42; hex: 0x2a; oct: 052; bin: 0b101010&quot;</span>
769 </pre></div>
770 </div>
771 <p>Padded hex byte with prefix and always prints both hex characters:</p>
772 <div class="highlight-c++ notranslate"><div class="highlight"><pre><span></span><span class="n">fmt</span><span class="o">::</span><span class="n">format</span><span class="p">(</span><span class="s">&quot;{:#04x}&quot;</span><span class="p">,</span><span class="w"> </span><span class="mi">0</span><span class="p">);</span>
773 <span class="c1">// Result: &quot;0x00&quot;</span>
774 </pre></div>
775 </div>
776 <p>Box drawing using Unicode fill:</p>
777 <div class="highlight-c++ notranslate"><div class="highlight"><pre><span></span><span class="n">fmt</span><span class="o">::</span><span class="n">print</span><span class="p">(</span>
778 <span class="w"> </span><span class="s">&quot;┌{0:─^{2}}┐</span><span class="se">\n</span><span class="s">&quot;</span>
779 <span class="w"> </span><span class="s">&quot;│{1: ^{2}}│</span><span class="se">\n</span><span class="s">&quot;</span>
780 <span class="w"> </span><span class="s">&quot;└{0:─^{2}}┘</span><span class="se">\n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;&quot;</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;Hello, world!&quot;</span><span class="p">,</span><span class="w"> </span><span class="mi">20</span><span class="p">);</span>
781 </pre></div>
782 </div>
783 <p>prints:</p>
784 <div class="highlight-c++ notranslate"><div class="highlight"><pre><span></span>┌────────────────────┐
785 │ Hello, world! │
786 └────────────────────┘
787 </pre></div>
788 </div>
789 <p>Using type-specific formatting:</p>
790 <div class="highlight-c++ notranslate"><div class="highlight"><pre><span></span><span class="cp">#include</span><span class="w"> </span><span class="cpf">&lt;fmt/chrono.h&gt;</span>
791
792 <span class="k">auto</span><span class="w"> </span><span class="n">t</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">tm</span><span class="p">();</span>
793 <span class="n">t</span><span class="p">.</span><span class="n">tm_year</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">2010</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="mi">1900</span><span class="p">;</span>
794 <span class="n">t</span><span class="p">.</span><span class="n">tm_mon</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">7</span><span class="p">;</span>
795 <span class="n">t</span><span class="p">.</span><span class="n">tm_mday</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">4</span><span class="p">;</span>
796 <span class="n">t</span><span class="p">.</span><span class="n">tm_hour</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">12</span><span class="p">;</span>
797 <span class="n">t</span><span class="p">.</span><span class="n">tm_min</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">15</span><span class="p">;</span>
798 <span class="n">t</span><span class="p">.</span><span class="n">tm_sec</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">58</span><span class="p">;</span>
799 <span class="n">fmt</span><span class="o">::</span><span class="n">print</span><span class="p">(</span><span class="s">&quot;{:%Y-%m-%d %H:%M:%S}&quot;</span><span class="p">,</span><span class="w"> </span><span class="n">t</span><span class="p">);</span>
800 <span class="c1">// Prints: 2010-08-04 12:15:58</span>
801 </pre></div>
802 </div>
803 <p>Using the comma as a thousands separator:</p>
804 <div class="highlight-c++ notranslate"><div class="highlight"><pre><span></span><span class="cp">#include</span><span class="w"> </span><span class="cpf">&lt;fmt/format.h&gt;</span>
805
806 <span class="k">auto</span><span class="w"> </span><span class="n">s</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">fmt</span><span class="o">::</span><span class="n">format</span><span class="p">(</span><span class="n">std</span><span class="o">::</span><span class="n">locale</span><span class="p">(</span><span class="s">&quot;en_US.UTF-8&quot;</span><span class="p">),</span><span class="w"> </span><span class="s">&quot;{:L}&quot;</span><span class="p">,</span><span class="w"> </span><span class="mi">1234567890</span><span class="p">);</span>
807 <span class="c1">// s == &quot;1,234,567,890&quot;</span>
808 </pre></div>
809 </div>
810 </section>
811 </section>
812
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