wcstod(), wcstof(), wcstold()

Convert a string to a 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 );

Library:

libc

Description:

These functions convert a string to a number: The wcstod() function converts the string pointed to by ptr to double representation; wcstof() converts to a float; wcstold() to a long double. The function recognizes a string 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 function expects the subject 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.

Because 0 is a valid return that is also used for an error, errno should be set to 0 before calling these functions, then checked 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

See also:

errno

"String manipulation functions" and "Wide-character functions" in the summary of functions chapter.