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wcstod, wcstof, wcstold: porovnat široké znaky v paměti

Originální popis anglicky:
wcstod, wcstof, wcstold - convert a wide-character string to a double-precision
number

Návod, kniha: POSIX Programmer's Manual## STRUČNĚ

**#include <wchar.h>**
double wcstod(const wchar_t *restrict ** ***nptr***, wchar_t
**restrict** *endptr***);**
float wcstof(const wchar_t *restrict ** ***nptr***, wchar_t
**restrict** *endptr***);**
long double wcstold(const wchar_t *restrict ** ***nptr***,**
wchar_t **restrict **
***endptr* **);**
## POPIS / INSTRUKCE

These functions shall convert the initial portion of the wide-character string
pointed to by *nptr* to **double**, **float**, and **long
double** representation, respectively. First, they shall decompose the input
wide-character string into three parts:
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.
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(
*n-wchar-sequence_opt*) 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 *n*-wchar sequences is
implementation-defined. A pointer to the final wide string shall be stored in
the object pointed to by *endptr*, provided that *endptr* is not a
null pointer.
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.
The radix character shall be as defined in the program's locale (category
*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 (
**'.'** ).
In other than the C or POSIX locales, other implementation-defined
subject sequences may be accepted.
If the subject sequence is empty or does not have the expected form, no
conversion shall be performed; the value of *nptr* shall be stored in the
object pointed to by *endptr*, provided that *endptr* is not a null
pointer.
The *wcstod*() function shall not change the setting of *errno* if
successful.
Since 0 is returned on error and is also a valid return on success, an
application wishing to check for error situations should set *errno* to
0, then call *wcstod*(), *wcstof*(), or *wcstold*(), then check
*errno*.
## NÁVRATOVÁ HODNOTA

Upon successful completion, these functions shall return the converted value. If
no conversion could be performed, 0 shall be returned and *errno*
may be set to [EINVAL].
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 *errno* shall be set to
[ERANGE].
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 *errno* set to [ERANGE].
## CHYBY / ERRORY

The *wcstod*() function shall fail if:
*wcstod*() function may fail if:
*The following sections are informative.*
## PŘÍKLADY POUŽITÍ

None.
## 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.
If the subject sequence has the decimal form and at most DECIMAL_DIG (defined in
*<float.h>*) significant digits, the result should be correctly
rounded. If the subject sequence *D* has the decimal form and more than
DECIMAL_DIG significant digits, consider the two bounding, adjacent decimal
strings *L* and *U*, both having DECIMAL_DIG significant digits,
such that the values of *L*, *D*, and *U* satisfy **"L
<= D <= U"** . The result should be one of the (equal or
adjacent) values that would be obtained by correctly rounding *L* and
*U* according to the current rounding direction, with the extra
stipulation that the error with respect to *D* should have a correct sign
for the current rounding direction.
## RATIONALE

None.
## FUTURE
DIRECTIONS

None.
## SOUVISEJÍCÍ

*iswspace*() , *localeconv*() , *scanf*() , *setlocale*() ,
*wcstol*() , the Base Definitions volume of
IEEE Std 1003.1-2001, Chapter 7, Locale, *<float.h>*,
*<wchar.h>*
## 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
.

Návod, kniha: POSIX Programmer's Manual

- 1.
- An initial, possibly empty, sequence of white-space
wide-character codes (as specified by
*iswspace*())

- 2.
- A subject sequence interpreted as a floating-point constant or representing infinity or NaN

- 3.
- 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

- *
- A non-empty sequence of decimal digits optionally containing a radix character, then an optional exponent part

- *
- A 0x or 0X, then a non-empty sequence of hexadecimal digits optionally containing a radix character, then an optional binary exponent part

- *
- One of INF or INFINITY, or any other wide string equivalent except for case

- *
- One of NAN or NAN(
*n-wchar-sequence_opt*), or any other wide string ignoring case in the NAN part, where:

n-wchar-sequence:digitnondigitn-wchar-sequence digitn-wchar-sequence nondigit

**ERANGE**- The value to be returned would cause overflow or underflow.

**EINVAL**- No conversion could be performed.

2003 | IEEE/The Open Group |

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