2004-11-03 13:51:07 +00:00
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.\" Copyright (c) 2001-2003 The Open Group, All Rights Reserved
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2007-06-20 22:33:04 +00:00
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.TH "WCSTOD" 3P 2003 "IEEE/The Open Group" "POSIX Programmer's Manual"
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2004-11-03 13:51:07 +00:00
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.\" wcstod
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2007-09-20 06:03:25 +00:00
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.SH PROLOG
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This manual page is part of the POSIX Programmer's Manual.
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The Linux implementation of this interface may differ (consult
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the corresponding Linux manual page for details of Linux behavior),
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or the interface may not be implemented on Linux.
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2004-11-03 13:51:07 +00:00
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.SH NAME
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wcstod, wcstof, wcstold \- convert a wide-character string to a double-precision
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number
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.SH SYNOPSIS
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.LP
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\fB#include <wchar.h>
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.br
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.sp
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double wcstod(const wchar_t *restrict\fP \fInptr\fP\fB, wchar_t **restrict\fP
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\fIendptr\fP\fB);
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.br
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float wcstof(const wchar_t *restrict\fP \fInptr\fP\fB, wchar_t **restrict\fP
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\fIendptr\fP\fB);
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.br
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long double wcstold(const wchar_t *restrict\fP \fInptr\fP\fB,
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.br
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\ \ \ \ \ \ wchar_t **restrict\fP \fIendptr\fP\fB);
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.br
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\fP
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.SH DESCRIPTION
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.LP
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These functions shall convert the initial portion of the wide-character
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string pointed to by \fInptr\fP to \fBdouble\fP,
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\fBfloat\fP, and \fBlong double\fP representation, respectively. First,
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they shall decompose the input wide-character string into
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three parts:
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.IP " 1." 4
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An initial, possibly empty, sequence of white-space wide-character
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codes (as specified by \fIiswspace\fP())
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.LP
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.IP " 2." 4
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A subject sequence interpreted as a floating-point constant or representing
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infinity or NaN
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.LP
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.IP " 3." 4
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A final wide-character string of one or more unrecognized wide-character
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codes, including the terminating null wide-character
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code of the input wide-character string
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.LP
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.LP
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Then they shall attempt to convert the subject sequence to a floating-point
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number, and return the result.
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.LP
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The expected form of the subject sequence is an optional plus or minus
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sign, then one of the following:
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.IP " *" 3
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A non-empty sequence of decimal digits optionally containing a radix
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character, then an optional exponent part
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.LP
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.IP " *" 3
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A 0x or 0X, then a non-empty sequence of hexadecimal digits optionally
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containing a radix character, then an optional binary
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exponent part
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.LP
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.IP " *" 3
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One of INF or INFINITY, or any other wide string equivalent except
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for case
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.LP
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.IP " *" 3
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One of NAN or NAN(\fIn-wchar-sequence_opt\fP), or any other wide string
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ignoring case in the NAN part,
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where:
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.sp
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.RS
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.nf
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\fBn-wchar-sequence:
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digit
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nondigit
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n-wchar-sequence digit
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n-wchar-sequence nondigit
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\fP
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.fi
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.RE
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.LP
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.LP
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The subject sequence is defined as the longest initial subsequence
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of the input wide string, starting with the first
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non-white-space wide character, that is of the expected form. The
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subject sequence contains no wide characters if the input wide
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string is not of the expected form.
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.LP
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If the subject sequence has the expected form for a floating-point
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number, the sequence of wide characters starting with the
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first digit or the radix character (whichever occurs first) shall
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be interpreted as a floating constant according to the rules of
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the C language, except that the radix character shall be used in place
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of a period, and that if neither an exponent part nor a
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radix character appears in a decimal floating-point number, or if
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a binary exponent part does not appear in a hexadecimal
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floating-point number, an exponent part of the appropriate type with
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value zero shall be assumed to follow the last digit in the
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string. If the subject sequence begins with a minus sign, the sequence
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shall be interpreted as negated. A wide-character sequence
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INF or INFINITY shall be interpreted as an infinity, if representable
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in the return type, else as if it were a floating constant
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that is too large for the range of the return type. A wide-character
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sequence NAN or
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NAN(\fIn-wchar-sequence_opt\fP) shall be interpreted as a quiet NaN,
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if supported in the return type,
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else as if it were a subject sequence part that does not have the
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expected form; the meaning of the \fIn\fP-wchar sequences is
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implementation-defined. A pointer to the final wide string shall be
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stored in the object pointed to by \fIendptr\fP, provided that
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\fIendptr\fP is not a null pointer.
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.LP
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If the subject sequence has the hexadecimal form and FLT_RADIX is
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a power of 2, the conversion shall be rounded in an
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implementation-defined manner.
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.LP
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The
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radix character shall be as defined in the program's locale (category
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\fILC_NUMERIC ).\fP In the POSIX locale, or in a locale
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where the radix character is not defined, the radix character shall
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default to a period ( \fB'.'\fP ).
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.LP
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In other than the C \ or POSIX locales, other
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implementation-defined subject sequences may be accepted.
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.LP
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If the subject sequence is empty or does not have the expected form,
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no conversion shall be performed; the value of \fInptr\fP
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shall be stored in the object pointed to by \fIendptr\fP, provided
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that \fIendptr\fP is not a null pointer.
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.LP
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The
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\fIwcstod\fP() function shall not change the setting of \fIerrno\fP
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if successful.
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.LP
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Since 0 is returned on error and is also a valid return on success,
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an application wishing to check for error situations should
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set \fIerrno\fP to 0, then call \fIwcstod\fP(), \fIwcstof\fP(), or
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\fIwcstold\fP(), then check \fIerrno\fP.
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.SH RETURN VALUE
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.LP
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Upon successful completion, these functions shall return the converted
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value. If no conversion could be performed, 0 shall be
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returned \ and \fIerrno\fP may be set to [EINVAL].
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.LP
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If the correct value is outside the range of representable values,
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\(+-HUGE_VAL, \(+-HUGE_VALF, or \(+-HUGE_VALL
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shall be returned (according to the sign of the value), and \fIerrno\fP
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shall be set to [ERANGE].
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.LP
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If the correct value would cause underflow, a value whose magnitude
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is no greater than the smallest normalized positive number
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in the return type shall be returned and \fIerrno\fP set to [ERANGE].
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.SH ERRORS
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.LP
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The \fIwcstod\fP() function shall fail if:
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.TP 7
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.B ERANGE
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The value to be returned would cause overflow or underflow.
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.sp
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.LP
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The \fIwcstod\fP() function may fail if:
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.TP 7
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.B EINVAL
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No
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conversion could be performed.
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.sp
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.LP
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\fIThe following sections are informative.\fP
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.SH EXAMPLES
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.LP
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None.
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.SH APPLICATION USAGE
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.LP
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If the subject sequence has the hexadecimal form and FLT_RADIX is
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not a power of 2, and the result is not exactly representable,
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the result should be one of the two numbers in the appropriate internal
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format that are adjacent to the hexadecimal floating source
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value, with the extra stipulation that the error should have a correct
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sign for the current rounding direction.
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.LP
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If the subject sequence has the decimal form and at most DECIMAL_DIG
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(defined in \fI<float.h>\fP) significant digits, the result should
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be correctly rounded. If the subject
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sequence \fID\fP has the decimal form and more than DECIMAL_DIG significant
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digits, consider the two bounding, adjacent decimal
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strings \fIL\fP and \fIU\fP, both having DECIMAL_DIG significant digits,
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such that the values of \fIL\fP, \fID\fP, and \fIU\fP
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satisfy \fB"L <= D <= U"\fP . The result should be one of the (equal
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or adjacent) values that would be obtained by
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correctly rounding \fIL\fP and \fIU\fP according to the current rounding
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direction, with the extra stipulation that the error
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with respect to \fID\fP should have a correct sign for the current
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rounding direction.
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.SH RATIONALE
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.LP
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None.
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.SH FUTURE DIRECTIONS
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.LP
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None.
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.SH SEE ALSO
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.LP
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2007-09-20 06:11:55 +00:00
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\fIiswspace\fP(), \fIlocaleconv\fP(), \fIscanf\fP(), \fIsetlocale\fP()
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, \fIwcstol\fP(), the
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2004-11-03 13:51:07 +00:00
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Base Definitions volume of IEEE\ Std\ 1003.1-2001, Chapter 7, Locale,
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\fI<float.h>\fP, \fI<wchar.h>\fP
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.SH COPYRIGHT
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Portions of this text are reprinted and reproduced in electronic form
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from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
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-- Portable Operating System Interface (POSIX), The Open Group Base
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Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of
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Electrical and Electronics Engineers, Inc and The Open Group. In the
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event of any discrepancy between this version and the original IEEE and
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The Open Group Standard, the original IEEE and The Open Group Standard
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is the referee document. The original Standard can be obtained online at
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http://www.opengroup.org/unix/online.html .
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