nan, nanf, nanl, nand32, nand64, nand128

float       nanf( const char* arg );

double      nan( const char* arg );

long double nanl( const char* arg );

_Decimal32  nand32( const char* arg );

_Decimal64  nand64( const char* arg );

_Decimal128 nand128( const char* arg );

Converts the implementation-defined character string arg into the corresponding quiet NaN value, as if by calling the appropriate parsing function strtoX, as follows:

• The call nan("n-char-sequence"), where n-char-sequence is a sequence of digits, Latin letters, and underscores, is equivalent to the call /*strtoX*/("NAN(n-char-sequence)", (char**)NULL);.
• The call nan("") is equivalent to the call /*strtoX*/("NAN()", (char**)NULL);.
• The call nan("string"), where string is neither an n-char-sequence nor an empty string, is equivalent to the call /*strtoX*/("NAN", (char**)NULL);.

Parameters

Return value

The quiet NaN value that corresponds to the identifying string arg or zero if the implementation does not support quiet NaNs.

If the implementation supports IEEE floating-point arithmetic (IEC 60559), it also supports quiet NaNs.

Error handling

This function is not subject to any of the error conditions specified in math_errhandling.

Example

#include <stdio.h>
#include <math.h>
#include <stdint.h>
#include <inttypes.h>
#include <string.h>
 
int main(void)
{
    double f1 = nan("1");
    uint64_t f1n; memcpy(&f1n, &f1, sizeof f1);
    printf("nan(\"1\")   = %f (%" PRIx64 ")\n", f1, f1n);
 
    double f2 = nan("2");
    uint64_t f2n; memcpy(&f2n, &f2, sizeof f2);
    printf("nan(\"2\")   = %f (%" PRIx64 ")\n", f2, f2n);
 
    double f3 = nan("0xF");
    uint64_t f3n; memcpy(&f3n, &f3, sizeof f3);
    printf("nan(\"0xF\") = %f (%" PRIx64 ")\n", f3, f3n);
}

nan("1")   = nan (7ff8000000000001)
nan("2")   = nan (7ff8000000000002)
nan("0xF") = nan (7ff800000000000f)

References

• C17 standard (ISO/IEC 9899:2018):
• 7.12.11.2 The nan functions (p: 186-187)
• F.10.8.2 The nan functions (p: 386)
• C11 standard (ISO/IEC 9899:2011):
• 7.12.11.2 The nan functions (p: 256)
• F.10.8.2 The nan functions (p: 529)
• C99 standard (ISO/IEC 9899:1999):
• 7.12.11.2 The nan functions (p: 237)
• F.9.8.2 The fabs functions (p: 465)

See also