wcstod.3p (8880B)
- '\" et
- .TH WCSTOD "3P" 2017 "IEEE/The Open Group" "POSIX Programmer's Manual"
- .\"
- .SH PROLOG
- This manual page is part of the POSIX Programmer's Manual.
- The Linux implementation of this interface may differ (consult
- the corresponding Linux manual page for details of Linux behavior),
- or the interface may not be implemented on Linux.
- .\"
- .SH NAME
- wcstod,
- wcstof,
- wcstold
- \(em convert a wide-character string to a double-precision number
- .SH SYNOPSIS
- .LP
- .nf
- #include <wchar.h>
- .P
- double wcstod(const wchar_t *restrict \fInptr\fP, wchar_t **restrict \fIendptr\fP);
- float wcstof(const wchar_t *restrict \fInptr\fP, wchar_t **restrict \fIendptr\fP);
- long double wcstold(const wchar_t *restrict \fInptr\fP,
- wchar_t **restrict \fIendptr\fP);
- .fi
- .SH DESCRIPTION
- The functionality described on this reference page is aligned with the
- ISO\ C standard. Any conflict between the requirements described here and the
- ISO\ C standard is unintentional. This volume of POSIX.1\(hy2017 defers to the ISO\ C standard.
- .P
- These functions shall convert the initial portion of the wide-character
- string pointed to by
- .IR nptr
- to
- .BR double ,
- .BR float ,
- and
- .BR "long double"
- representation, respectively. First, they shall decompose the input
- wide-character string into three parts:
- .IP " 1." 4
- An initial, possibly empty, sequence of white-space wide-character
- codes (as specified by
- \fIiswspace\fR())
- .IP " 2." 4
- A subject sequence interpreted as a floating-point constant or
- representing infinity or NaN
- .IP " 3." 4
- A final wide-character string of one or more unrecognized wide-character
- codes, including the terminating null wide-character code of the input
- wide-character string
- .P
- Then they shall attempt to convert the subject sequence to a
- floating-point number, and return the result.
- .P
- The expected form of the subject sequence is an optional
- .BR '+'
- or
- .BR '\-'
- sign, then one of the following:
- .IP " *" 4
- A non-empty sequence of decimal digits optionally containing a radix
- character; then an optional exponent part consisting of the wide
- character
- .BR 'e'
- or the wide character
- .BR 'E' ,
- optionally followed by a
- .BR '+'
- or
- .BR '\-'
- wide character, and then followed by one or more decimal digits
- .IP " *" 4
- A 0x or 0X, then a non-empty sequence of hexadecimal digits optionally
- containing a radix character; then an optional binary exponent part
- consisting of the wide character
- .BR 'p'
- or the wide character
- .BR 'P' ,
- optionally followed by a
- .BR '+'
- or
- .BR '\-'
- wide character, and then followed by one or more decimal digits
- .IP " *" 4
- One of INF or INFINITY, or any other wide string equivalent except for
- case
- .IP " *" 4
- One of NAN or NAN(\fIn-wchar-sequence\s-3\dopt\u\s+3\fR), or any other
- wide string ignoring case in the NAN part, where:
- .RS 4
- .sp
- .RS 4
- .nf
- n-wchar-sequence:
- digit
- nondigit
- n-wchar-sequence digit
- n-wchar-sequence nondigit
- .fi
- .P
- .RE
- .RE
- .P
- The subject sequence is defined as the longest initial subsequence of
- the input wide string, starting with the first non-white-space wide
- character, that is of the expected form. The subject sequence contains
- no wide characters if the input wide string is not of the expected
- form.
- .P
- If the subject sequence has the expected form for a floating-point
- number, the sequence of wide characters starting with the first digit
- or the radix character (whichever occurs first) shall be interpreted as
- a floating constant according to the rules of the C language, except
- that the radix character shall be used in place of a period, and that
- if neither an exponent part nor a radix character appears in a decimal
- floating-point number, or if a binary exponent part does not appear in
- a hexadecimal floating-point number, an exponent part of the
- appropriate type with value zero shall be assumed to follow the last
- digit in the string. If the subject sequence begins with a
- <hyphen-minus>,
- the sequence shall be interpreted as negated. A wide-character sequence
- INF or INFINITY shall be interpreted as an infinity, if representable
- in the return type, else as if it were a floating constant that is too
- large for the range of the return type. A wide-character sequence NAN
- or NAN(\fIn-wchar-sequence\s-3\dopt\u\s+3\fR) shall be interpreted as a
- quiet NaN, if supported in the return type, else as if it were a
- subject sequence part that does not have the expected form; the meaning
- of the \fIn\fP-wchar sequences is implementation-defined. A pointer to
- the final wide string shall be stored in the object pointed to by
- .IR endptr ,
- provided that
- .IR endptr
- is not a null pointer.
- .P
- If the subject sequence has the hexadecimal form and FLT_RADIX is a
- power of 2, the conversion shall be rounded in an
- implementation-defined manner.
- .P
- The radix character shall be as defined in the current locale
- (category
- .IR LC_NUMERIC ).
- In the POSIX locale, or in a locale where the radix character is not
- defined, the radix character shall default to a
- <period>
- (\c
- .BR '.' ).
- .P
- In other than the C
- or POSIX
- locale, additional locale-specific subject sequence forms may be
- accepted.
- .P
- If the subject sequence is empty or does not have the expected form, no
- conversion shall be performed; the value of
- .IR nptr
- shall be stored in the object pointed to by
- .IR endptr ,
- provided that
- .IR endptr
- is not a null pointer.
- .P
- These functions shall not change the setting of
- .IR errno
- if successful.
- .P
- Since 0 is returned on error and is also a valid return on success,
- an application wishing to check for error situations should set
- .IR errno
- to 0, then call
- \fIwcstod\fR(),
- \fIwcstof\fR(),
- or
- \fIwcstold\fR(),
- then check
- .IR errno .
- .SH "RETURN VALUE"
- Upon successful completion, these functions shall return the converted
- value. If no conversion could be performed, 0 shall be returned
- and
- .IR errno
- may be set to
- .BR [EINVAL] .
- .P
- If the correct value is outside the range of representable values,
- \(+-HUGE_VAL, \(+-HUGE_VALF, or \(+-HUGE_VALL shall be returned
- (according to the sign of the value), and
- .IR errno
- shall be set to
- .BR [ERANGE] .
- .P
- If the correct value would cause underflow, a value whose magnitude is
- no greater than the smallest normalized positive number in the return
- type shall be returned and
- .IR errno
- set to
- .BR [ERANGE] .
- .SH ERRORS
- The
- \fIwcstod\fR()
- function shall fail if:
- .TP
- .BR ERANGE
- The value to be returned would cause overflow or underflow.
- .P
- The
- \fIwcstod\fR()
- function may fail if:
- .TP
- .BR EINVAL
- No conversion could be performed.
- .LP
- .IR "The following sections are informative."
- .SH EXAMPLES
- None.
- .SH "APPLICATION USAGE"
- If the subject sequence has the hexadecimal form and FLT_RADIX is not a
- power of 2, and the result is not exactly representable, the result
- should be one of the two numbers in the appropriate internal format
- that are adjacent to the hexadecimal floating source value, with the
- extra stipulation that the error should have a correct sign for the
- current rounding direction.
- .P
- If the subject sequence has the decimal form and at most DECIMAL_DIG
- (defined in
- .IR <float.h> )
- significant digits, the result should be correctly rounded. If the
- subject sequence \fID\fP has the decimal form and more than DECIMAL_DIG
- significant digits, consider the two bounding, adjacent decimal strings
- \fIL\fP and \fIU\fP, both having DECIMAL_DIG significant digits, such
- that the values of \fIL\fP, \fID\fP, and \fIU\fP satisfy
- .BR \(dqL <= D <= U\(dq .
- The result should be one of the (equal or adjacent) values that would
- be obtained by correctly rounding \fIL\fP and \fIU\fP according to the
- current rounding direction, with the extra stipulation that the error
- with respect to \fID\fP should have a correct sign for the current
- rounding direction.
- .SH RATIONALE
- None.
- .SH "FUTURE DIRECTIONS"
- None.
- .SH "SEE ALSO"
- .IR "\fIfscanf\fR\^(\|)",
- .IR "\fIiswspace\fR\^(\|)",
- .IR "\fIlocaleconv\fR\^(\|)",
- .IR "\fIsetlocale\fR\^(\|)",
- .IR "\fIwcstol\fR\^(\|)"
- .P
- The Base Definitions volume of POSIX.1\(hy2017,
- .IR "Chapter 7" ", " "Locale",
- .IR "\fB<float.h>\fP",
- .IR "\fB<wchar.h>\fP"
- .\"
- .SH COPYRIGHT
- Portions of this text are reprinted and reproduced in electronic form
- from IEEE Std 1003.1-2017, Standard for Information Technology
- -- Portable Operating System Interface (POSIX), The Open Group Base
- Specifications Issue 7, 2018 Edition,
- Copyright (C) 2018 by the Institute of
- Electrical and Electronics Engineers, Inc and The Open Group.
- In the event of any discrepancy between this version and the original IEEE and
- The Open Group Standard, the original IEEE and The Open Group Standard
- is the referee document. The original Standard can be obtained online at
- http://www.opengroup.org/unix/online.html .
- .PP
- Any typographical or formatting errors that appear
- in this page are most likely
- to have been introduced during the conversion of the source files to
- man page format. To report such errors, see
- https://www.kernel.org/doc/man-pages/reporting_bugs.html .