wcstod(), wcstof(), wcstold()

QNX SDP8.0C Library ReferenceAPIDeveloper

Convert a wide-character string into a double, float, or long double

Synopsis:

#include <wchar.h>

double wcstod( const wchar_t * ptr,
               wchar_t ** endptr );

float wcstof( const wchar_t * ptr,
              wchar ** endptr );

long double wcstold( const wchar_t * ptr,
                     wchar ** endptr );

Arguments:

nptr: A pointer to the string to parse.
endptr: If this argument isn't NULL, the function stores in it a pointer to the first unrecognized character found in the string.

Library:

libc

Use the -l c option to qcc to link against this library. This library is usually included automatically.

Description:

These functions convert a wide-character string to a number:

wcstod() function converts it to a double
wcstof() converts it to a float
wcstold() to a long double

These functions recognize strings containing the following:

optional white space
an optional plus or minus sign
a sequence of digits containing an optional decimal point
an optional e or E, followed by an optionally signed sequence of digits

The functions expect the string to have a plus or minus sign, followed by one of these forms:

a sequence of decimal digits, optionally followed by a radix character, optionally followed by an exponent part
a 0x or 0X followed by a sequence of hexadecimal digits, optionally followed by a radix character, optionally followed by a binary exponent part
the case-insensitive string INF or INFINITY
the case-insensitive string NAN or NAN(n-wchar-sequence), where n-wchar-sequence may be a digit, a nondigit, a n-wchar-sequence digit, or a n-wchar-sequence nondigit

The value is correctly rounded if the subject is hexadecimal and FLT_RADIX is 2.

The radix character is locale specific, depending upon LC_NUMERIC.

The conversion ends at the first unrecognized character. If endptr isn't NULL, a pointer to the unrecognized wide character is stored in the object endptr points to.

Note:

Because 0 is a valid return that is also used for an error, you should set errno to 0 before calling these functions, and check errno again afterward. These functions don't change errno on success.

Returns:

The converted value. If the correct value would cause overflow, plus or minus HUGE_VAL is returned according to the sign, and errno is set to ERANGE. If the correct value would cause underflow, then zero is returned, and errno is set to ERANGE.

Zero is returned when the input string can't be converted. When an error occurs, errno indicates the error detected.

Classification:

ANSI, POSIX 1003.1


Safety:
Cancellation point	No
Signal handler	Yes
Thread	Yes

Page updated: August 09, 2024