strtod32() - strtod64() - strtod128() — Convert Character String to Decimal Floating-Point

Format

#define __STDC_WANT_DEC_FP__
#include <stdlib.h>
_Decimal32 strtod32(const char *nptr, char **endptr);
_Decimal64 strtod64(const char *nptr, char **endptr);
_Decimal128 strtod132(const char *nptr, char **endptr);

Language Level

ANSI

Threadsafe

Yes

Locale Sensitive

The behavior of these functions might be affected by the LC_CTYPE and LC_NUMERIC categories of the current locale. For more information, see Understanding CCSIDs and Locales.

Description

The strtod32(), strtod64(), and strtod128() functions convert a character string to a single-precision, double-precision, or quad-precision decimal floating-point value. The parameter nptr points to a sequence of characters that can be interpreted as a numeric decimal floating-point value. These functions stop reading the string at the first character that is not recognized as part of a number. This character can be the null character at the end of the string. The endptr parameter is updated to point to this character, provided that endptr is not a NULL pointer.

The strtod32(), strtod64(), and strtod128() functions expect nptr to point to a string with the following form:

The first character that does not fit this form stops the scan. In addition, a sequence of INFINITY or NAN (ignoring case) is allowed.

Return Value

The strtod32(), strtod64(), and strtod128() functions return the value of the floating-point number, except when the representation causes an underflow or overflow. For an overflow, strtod32() returns HUGE_VAL_D32 or -HUGE_VAL_D32; strtod64() returns HUGE_VAL_D64 or -HUGE_VAL_D64; strtod128() returns HUGE_VAL_D128 or -HUGE_VAL_D128. For an underflow, all functions return +0.E0.

In both the overflow and underflow cases, errno is set to ERANGE. If the string pointed to by nptr does not have the expected form, a value of +0.E0 is returned and the value of nptr is stored in the object pointed to by endptr, provided that endptr is not a NULL pointer.

The strtod32(), strtod64(), and strtod128() functions do not fail if a character other than a digit follows an E or e that is read as an exponent. For example, 100elf is converted to the floating-point value 100.0.

A character sequence of INFINITY (ignoring case) yields a value of INFINITY. A character value of NAN yields a Quiet Not-A-Number (NaN) value.

If necessary, the return value is rounded using the rounding mode Round to Nearest, Ties to Even.

Example

This example converts the strings to single-precision, double-precision, and quad-precision decimal floating-point values. It prints the converted values and the substring that stopped the conversion.


#define __STDC_WANT_DEC_FP__
#include <stdlib.h>
#include <stdio.h>
 
int main(void)
{
   char *string, *stopstring;
   _Decimal32 d32;
   _Decimal64 d64;
   _Decimal128 d128;
 
   string = "3.1415926This stopped it";
   d32 = strtod32(string, &stopstring); 
   printf("string = %s\n", string);
   printf(" strtod32 = %Hf\n", d32);
   printf(" Stopped scan at %s\n\n", stopstring); 
   string = "100ergs"; 
   d32 = strtod32(string, &stopstring); 
   printf("string = \"%s\"\n", string);
   printf(" strtof = %Hf\n", d32); 
   printf(" Stopped scan at \"%s\"\n\n", stopstring); 
  
   string = "3.1415926This stopped it";
   d64 = strtod64(string, &stopstring); 
   printf("string = %s\n", string); 
   printf(" strtod = %Df\n", d64); 
   printf(" Stopped scan at %s\n\n", stopstring); 
   string = "100ergs"; 
   d64 = strtod64(string, &stopstring); 
   printf("string = \"%s\"\n", string); 
   printf(" strtod = %Df\n", d64); 
   printf(" Stopped scan at \"%s\"\n\n", stopstring);

   string = "3.1415926This stopped it"; 
   d128 = strtod128(string, &stopstring); 
   printf("string = %s\n", string); 
   printf(" strtold = %DDf\n", d128); 
   printf(" Stopped scan at %s\n\n", stopstring); 
   string = "100ergs"; 
   d128 = strtod128(string, &stopstring); 
   printf("string = \"%s\"\n", string); 
   printf(" strtold = %DDf\n", d128); 
   printf(" Stopped scan at \"%s\"\n\n", stopstring);
}

/***************** Output should be similar to: ***************** 

string = 3.1415926This stopped it 
 strtof = 3.141593 
 Stopped scan at This stopped it 

string = "100ergs" 
 strtof = 100.000000 
 Stopped scan at "ergs"

string = 3.1415926This stopped it 
 strtod= 3.141593 
 Stopped scan at This stopped it 

string = "100ergs" 
 strtod = 100.000000 
 Stopped scan at "ergs"

string = 3.1415926This stopped it 
 strtold = 3.141593 
 Stopped scan at This stopped it 

string = "100ergs" 
 strtold = 100.000000 
 Stopped scan at "ergs"

*/