path: root/man3p/wcstod.3p

.\" Copyright (c) 2001-2003 The Open Group, All Rights Reserved 
.TH "WCSTOD" P 2003 "IEEE/The Open Group" "POSIX Programmer's Manual"
.\" wcstod 
.SH NAME
wcstod, wcstof, wcstold \- convert a wide-character string to a double-precision
number
.SH SYNOPSIS
.LP
\fB#include <wchar.h>
.br
.sp
double wcstod(const wchar_t *restrict\fP \fInptr\fP\fB, wchar_t **restrict\fP
\fIendptr\fP\fB);
.br
float wcstof(const wchar_t *restrict\fP \fInptr\fP\fB, wchar_t **restrict\fP
\fIendptr\fP\fB);
.br
long double wcstold(const wchar_t *restrict\fP \fInptr\fP\fB,
.br
\ \ \ \ \ \  wchar_t **restrict\fP \fIendptr\fP\fB);
.br
\fP
.SH DESCRIPTION
.LP
These functions shall convert the initial portion of the wide-character
string pointed to by \fInptr\fP to \fBdouble\fP,
\fBfloat\fP, and \fBlong double\fP 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\fP())
.LP
.IP " 2." 4
A subject sequence interpreted as a floating-point constant or representing
infinity or NaN
.LP
.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
.LP
.LP
Then they shall attempt to convert the subject sequence to a floating-point
number, and return the result.
.LP
The expected form of the subject sequence is an optional plus or minus
sign, then one of the following:
.IP " *" 3
A non-empty sequence of decimal digits optionally containing a radix
character, then an optional exponent part
.LP
.IP " *" 3
A 0x or 0X, then a non-empty sequence of hexadecimal digits optionally
containing a radix character, then an optional binary
exponent part
.LP
.IP " *" 3
One of INF or INFINITY, or any other wide string equivalent except
for case
.LP
.IP " *" 3
One of NAN or NAN(\fIn-wchar-sequence_opt\fP), or any other wide string
ignoring case in the NAN part,
where:
.sp
.RS
.nf

\fBn-wchar-sequence:
    digit
    nondigit
    n-wchar-sequence digit
    n-wchar-sequence nondigit
\fP
.fi
.RE
.LP
.LP
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.
.LP
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 minus sign, 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_opt\fP) 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 \fIendptr\fP, provided that
\fIendptr\fP is not a null pointer.
.LP
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.
.LP
The
radix character shall be as defined in the program's locale (category
\fILC_NUMERIC ).\fP In the POSIX locale, or in a locale
where the radix character is not defined, the radix character shall
default to a period ( \fB'.'\fP ). 
.LP
In other than the C   \ or POSIX  locales, other
implementation-defined subject sequences may be accepted.
.LP
If the subject sequence is empty or does not have the expected form,
no conversion shall be performed; the value of \fInptr\fP
shall be stored in the object pointed to by \fIendptr\fP, provided
that \fIendptr\fP is not a null pointer.
.LP
The
\fIwcstod\fP() function shall not change the setting of \fIerrno\fP
if successful.
.LP
Since 0 is returned on error and is also a valid return on success,
an application wishing to check for error situations should
set \fIerrno\fP to 0, then call \fIwcstod\fP(), \fIwcstof\fP(), or
\fIwcstold\fP(), then check \fIerrno\fP. 
.SH RETURN VALUE
.LP
Upon successful completion, these functions shall return the converted
value. If no conversion could be performed, 0 shall be
returned   \ and \fIerrno\fP may be set to [EINVAL]. 
.LP
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 \fIerrno\fP
shall be set to [ERANGE].
.LP
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 \fIerrno\fP set to [ERANGE].
.SH ERRORS
.LP
The \fIwcstod\fP() function shall fail if:
.TP 7
.B ERANGE
The value to be returned would cause overflow or underflow.
.sp
.LP
The \fIwcstod\fP() function may fail if:
.TP 7
.B EINVAL
No
conversion could be performed. 
.sp
.LP
\fIThe following sections are informative.\fP
.SH EXAMPLES
.LP
None.
.SH APPLICATION USAGE
.LP
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.
.LP
If the subject sequence has the decimal form and at most DECIMAL_DIG
(defined in \fI<float.h>\fP) 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 \fB"L <= D <= U"\fP . 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
.LP
None.
.SH FUTURE DIRECTIONS
.LP
None.
.SH SEE ALSO
.LP
\fIiswspace\fP() , \fIlocaleconv\fP() , \fIscanf\fP() , \fIsetlocale\fP()
, \fIwcstol\fP() , the
Base Definitions volume of IEEE\ Std\ 1003.1-2001, Chapter 7, Locale,
\fI<float.h>\fP, \fI<wchar.h>\fP
.SH COPYRIGHT
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
-- Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 6, Copyright (C) 2001-2003 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 .