174 lines
7.6 KiB
HTML
174 lines
7.6 KiB
HTML
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<title>ecvt</title>
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<basefont size="3"> <a name="ecvt"></a> <a name="tag_03_115"></a><!-- ecvt -->
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<!--header start-->
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<center><font size="2">The Open Group Base Specifications Issue 6<br>
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IEEE Std 1003.1-2001<br>
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Copyright © 2001 The IEEE and The Open Group, All Rights reserved.</font></center>
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<!--header end-->
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<hr size="2" noshade>
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<h4><a name="tag_03_115_01"></a>NAME</h4>
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<blockquote>ecvt, fcvt, gcvt - convert a floating-point number to a string (<b>LEGACY</b>)</blockquote>
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<h4><a name="tag_03_115_02"></a>SYNOPSIS</h4>
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<blockquote class="synopsis">
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<div class="box"><code><tt><sup>[<a href="javascript:open_code('XSI')">XSI</a>]</sup> <img src="../images/opt-start.gif" alt=
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"[Option Start]" border="0"> #include <<a href="../basedefs/stdlib.h.html">stdlib.h</a>><br>
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<br>
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char *ecvt(double</tt> <i>value</i><tt>, int</tt> <i>ndigit</i><tt>, int *restrict</tt> <i>decpt</i><tt>,<br>
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int *restrict</tt> <i>sign</i><tt>);<br>
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char *fcvt(double</tt> <i>value</i><tt>, int</tt> <i>ndigit</i><tt>, int *restrict</tt> <i>decpt</i><tt>,<br>
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int *restrict</tt> <i>sign</i><tt>);<br>
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char *gcvt(double</tt> <i>value</i><tt>, int</tt> <i>ndigit</i><tt>, char *</tt><i>buf</i><tt>); <img src="../images/opt-end.gif"
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alt="[Option End]" border="0"></tt></code></div>
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<tt><br>
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</tt></blockquote>
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<h4><a name="tag_03_115_03"></a>DESCRIPTION</h4>
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<blockquote>
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<p>The <i>ecvt</i>(), <i>fcvt</i>(), and <i>gcvt</i>() functions shall convert floating-point numbers to null-terminated
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strings.</p>
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<p>The <i>ecvt</i>() function shall convert <i>value</i> to a null-terminated string of <i>ndigit</i> digits (where <i>ndigit</i>
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is reduced to an unspecified limit determined by the precision of a <b>double</b>) and return a pointer to the string. The
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high-order digit shall be non-zero, unless the value is 0. The low-order digit shall be rounded in an implementation-defined
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manner. The position of the radix character relative to the beginning of the string shall be stored in the integer pointed to by
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<i>decpt</i> (negative means to the left of the returned digits). If <i>value</i> is zero, it is unspecified whether the integer
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pointed to by <i>decpt</i> would be 0 or 1. The radix character shall not be included in the returned string. If the sign of the
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result is negative, the integer pointed to by <i>sign</i> shall be non-zero; otherwise, it shall be 0.</p>
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<p>If the converted value is out of range or is not representable, the contents of the returned string are unspecified.</p>
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<p>The <i>fcvt</i>() function shall be equivalent to <i>ecvt</i>(), except that <i>ndigit</i> specifies the number of digits
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desired after the radix character. The total number of digits in the result string is restricted to an unspecified limit as
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determined by the precision of a <b>double</b>.</p>
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<p>The <i>gcvt</i>() function shall convert <i>value</i> to a null-terminated string (similar to that of the <tt>%g</tt> conversion
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specification format of <a href="../functions/printf.html"><i>printf</i>()</a>) in the array pointed to by <i>buf</i> and shall
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return <i>buf</i>. It shall produce <i>ndigit</i> significant digits (limited to an unspecified value determined by the precision
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of a <b>double</b>) in the <tt>%f</tt> conversion specification format of <a href="../functions/printf.html"><i>printf</i>()</a> if
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possible, or the <tt>%e</tt> conversion specification format of <a href="../functions/printf.html"><i>printf</i>()</a> (scientific
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notation) otherwise. A minus sign shall be included in the returned string if <i>value</i> is less than 0. A radix character shall
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be included in the returned string if <i>value</i> is not a whole number. Trailing zeros shall be suppressed where <i>value</i> is
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not a whole number. The radix character is determined by the current locale. If <a href=
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"../functions/setlocale.html"><i>setlocale</i>()</a> has not been called successfully, the default locale, POSIX, is used. The
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default locale specifies a period ( <tt>'.'</tt> ) as the radix character. The <i>LC_NUMERIC</i> category determines the value of
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the radix character within the current locale.</p>
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<p>These functions need not be reentrant. A function that is not required to be reentrant is not required to be thread-safe.</p>
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</blockquote>
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<h4><a name="tag_03_115_04"></a>RETURN VALUE</h4>
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<blockquote>
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<p>The <i>ecvt</i>() and <i>fcvt</i>() functions shall return a pointer to a null-terminated string of digits.</p>
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<p>The <i>gcvt</i>() function shall return <i>buf</i>.</p>
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<p>The return values from <i>ecvt</i>() and <i>fcvt</i>() may point to static data which may be overwritten by subsequent calls to
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these functions.</p>
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</blockquote>
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<h4><a name="tag_03_115_05"></a>ERRORS</h4>
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<blockquote>
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<p>No errors are defined.</p>
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</blockquote>
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<hr>
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<div class="box"><em>The following sections are informative.</em></div>
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<h4><a name="tag_03_115_06"></a>EXAMPLES</h4>
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<blockquote>
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<p>None.</p>
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</blockquote>
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<h4><a name="tag_03_115_07"></a>APPLICATION USAGE</h4>
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<blockquote>
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<p>The <a href="../functions/sprintf.html"><i>sprintf</i>()</a> function is preferred over this function.</p>
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</blockquote>
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<h4><a name="tag_03_115_08"></a>RATIONALE</h4>
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<blockquote>
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<p>None.</p>
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</blockquote>
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<h4><a name="tag_03_115_09"></a>FUTURE DIRECTIONS</h4>
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<blockquote>
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<p>These functions may be withdrawn in a future version.</p>
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</blockquote>
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<h4><a name="tag_03_115_10"></a>SEE ALSO</h4>
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<blockquote>
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<p><a href="printf.html"><i>printf</i>()</a> , <a href="setlocale.html"><i>setlocale</i>()</a> , the Base Definitions volume of
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IEEE Std 1003.1-2001, <a href="../basedefs/stdlib.h.html"><i><stdlib.h></i></a></p>
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</blockquote>
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<h4><a name="tag_03_115_11"></a>CHANGE HISTORY</h4>
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<blockquote>
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<p>First released in Issue 4, Version 2.</p>
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</blockquote>
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<h4><a name="tag_03_115_12"></a>Issue 5</h4>
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<blockquote>
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<p>Moved from X/OPEN UNIX extension to BASE.</p>
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<p>Normative text previously in the APPLICATION USAGE section is moved to the DESCRIPTION.</p>
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<p>A note indicating that these functions need not be reentrant is added to the DESCRIPTION.</p>
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</blockquote>
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<h4><a name="tag_03_115_13"></a>Issue 6</h4>
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<blockquote>
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<p>In the DESCRIPTION, the note about reentrancy is expanded to cover thread-safety.</p>
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<p>This function is marked LEGACY.</p>
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<p>The <b>restrict</b> keyword is added to the <i>ecvt</i>() and <i>fcvt</i>() prototypes for alignment with the
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ISO/IEC 9899:1999 standard.</p>
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<p>The DESCRIPTION is updated to explicitly use "conversion specification" to describe <tt>%g</tt> , <tt>%f</tt> , and
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<tt>%e</tt> .</p>
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</blockquote>
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<div class="box"><em>End of informative text.</em></div>
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POSIX ® is a registered Trademark of The IEEE.<br>
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