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| <title>GCC libquadmath: quadmath_snprintf</title> |
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| <a name="quadmath_005fsnprintf-_002d_002d_002d-Convert-to-string"></a> |
| <h3 class="section">3.2 <code>quadmath_snprintf</code> — Convert to string</h3> |
| |
| <p>The function <code>quadmath_snprintf</code> converts a <code>__float128</code> floating-point |
| number into a string. It is a specialized alternative to <code>snprintf</code>, where |
| the format string is restricted to a single conversion specifier with <code>Q</code> |
| modifier and conversion specifier <code>e</code>, <code>E</code>, <code>f</code>, <code>F</code>, <code>g</code>, |
| <code>G</code>, <code>a</code> or <code>A</code>, with no extra characters before or after the |
| conversion specifier. The <code>%m$</code> or <code>*m$</code> style must not be used in |
| the format. |
| </p> |
| <dl compact="compact"> |
| <dt>Syntax</dt> |
| <dd><p><code>int quadmath_snprintf (char *s, size_t size, const char *format, ...)</code> |
| </p> |
| </dd> |
| <dt><em>Arguments</em>:</dt> |
| <dd><table> |
| <tr><td width="15%"><var>s</var></td><td width="70%">output string</td></tr> |
| <tr><td width="15%"><var>size</var></td><td width="70%">byte size of the string, including tailing NUL</td></tr> |
| <tr><td width="15%"><var>format</var></td><td width="70%">conversion specifier string</td></tr> |
| </table> |
| |
| </dd> |
| <dt>Note</dt> |
| <dd><p>On some targets when supported by the C library hooks are installed |
| for <code>printf</code> family of functions, so that <code>printf ("%Qe", 1.2Q);</code> |
| etc. works too. |
| </p> |
| </dd> |
| <dt>Example</dt> |
| <dd><div class="smallexample"> |
| <pre class="smallexample">#include <quadmath.h> |
| #include <stdlib.h> |
| #include <stdio.h> |
| |
| int main () |
| { |
| __float128 r; |
| int prec = 20; |
| int width = 46; |
| char buf[128]; |
| |
| r = 2.0q; |
| r = sqrtq (r); |
| int n = quadmath_snprintf (buf, sizeof buf, "%+-#*.20Qe", width, r); |
| if ((size_t) n < sizeof buf) |
| printf ("%s\n", buf); |
| /* Prints: +1.41421356237309504880e+00 */ |
| quadmath_snprintf (buf, sizeof buf, "%Qa", r); |
| if ((size_t) n < sizeof buf) |
| printf ("%s\n", buf); |
| /* Prints: 0x1.6a09e667f3bcc908b2fb1366ea96p+0 */ |
| n = quadmath_snprintf (NULL, 0, "%+-#46.*Qe", prec, r); |
| if (n > -1) |
| { |
| char *str = malloc (n + 1); |
| if (str) |
| { |
| quadmath_snprintf (str, n + 1, "%+-#46.*Qe", prec, r); |
| printf ("%s\n", str); |
| /* Prints: +1.41421356237309504880e+00 */ |
| } |
| free (str); |
| } |
| return 0; |
| } |
| </pre></div> |
| |
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