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#include <stdlib.h> long double strtold(const char *s, char **endp); |
This function converts as many characters of s that look like a floating point number into that number. It also recognises (case-insensitively) "Inf", "Infinity", "NaN", "NaN(optional decimal-number), "NaN(optional octal-number) and "NaN(optional hex-number)". If endp is not a null pointer, a pointer to the first unconverted character will be stored in the location pointed to by endp.
The value represented by s.
If s is "Inf" or "Infinity", with any variations of case and
optionally prefixed with "+" or "-", the return value is
INFINITY
(if no prefix or a "+" prefix) or -INFINITY
(if the prefix is "-").
If s is "NaN" or "NaN()", with any variations of case and
optionally prefixed with "+" or "-", the return value is
(long double)NAN
. If the prefix is "-" the sign bit in the
NaN will be set to 1.
If s is "NaN(decimal-number)", "NaN(octal-number)"
or "NaN(hex-number)", with any variations of case
and optionally prefixed with "+" or "-", the return value is a NaN
with the mantissa bits set to the lower 63 bits
of decimal-number, octal-number or hex-number
and the most significant bit to 1 (the mantissa for long
doubles consists of 64 bits where the most significant bit is the
integer bit which must be set for NaNs). Use at most 16 hexadecimal
digits in hex-number or the internal conversion will overflow,
which results in a mantissa with all bits set. If the bit pattern
given is 0 (which won't work as a representation of a NaN) (long
double)NAN
will be returned. If the prefix is "-" the sign bit in
the NaN will be set to 1. Testing shows that SNaNs might be converted
into QNaNs (the second most significant bit will be set in the
mantissa).
ANSI/ISO C | C99 (see note 1); not C89 |
POSIX | 1003.1-2001; not 1003.2-1992 |
Notes:
char buf[] = "123ret"; char buf2[] = "0x123ret"; char buf3[] = "NAN(123)"; char buf4[] = "NAN(0x123)"; char *bp; long double x, x2, x3, x4; x = strtold(buf, &bp); x2 = strtold(buf2, &bp); x3 = strtold(buf3, &bp); x4 = strtold(buf4, &bp); |
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