_atodbl, _atodbl_l, _atoldbl, _atoldbl_l, _atoflt, _atoflt_l

Artikkel
08/27/2021
2 minutter å lese

Converts a string to a double (_atodbl), long double (_atoldbl), or float (_atoflt).

Syntax

int _atodbl( _CRT_DOUBLE * value, char * str );
int _atodbl_l ( _CRT_DOUBLE * value, char * str, _locale_t locale );
int _atoldbl( _LDOUBLE * value, char * str );
int _atoldbl_l ( _LDOUBLE * value, char * str, _locale_t locale );
int _atoflt( _CRT_FLOAT * value, const char * str );
int _atoflt_l( _CRT_FLOAT * value, const char * str, _locale_t locale );

Parameters

value
The double, long double, or float value that's produced by converting the string to a floating-point value. These values are wrapped in a structure.

str
The string to be parsed to convert into a floating-point value.

locale
The locale to use.

Return Value

Returns 0 if successful. Possible error codes are _UNDERFLOW or _OVERFLOW, which are defined in the header file <math.h>.

Remarks

These functions convert a string to a floating-point value. The difference between these functions and the atof family of functions is that these functions do not generate floating-point code and do not cause hardware exceptions. Instead, error conditions are reported as error codes.

If a string does not have a valid interpretation as a floating-point value, value is set to zero and the return value is zero.

The versions of these functions that have the _l suffix are identical the versions that don't have the suffix, except that they use the locale parameter that's passed in instead of the current thread locale.

By default, this function's global state is scoped to the application. To change this, see Global state in the CRT.

Requirements

Routines	Required header
_atodbl, _atoldbl, _atoflt _atodbl_l, _atoldbl_l, _atoflt_l	<stdlib.h>

Example

// crt_atodbl.c
// Uses _atodbl to convert a string to a double precision
// floating point value.

#include <stdlib.h>
#include <stdio.h>

int main()
{
   char str1[256] = "3.141592654";
   char abc[256] = "abc";
   char oflow[256] = "1.0E+5000";
   _CRT_DOUBLE dblval;
   _CRT_FLOAT fltval;
   int retval;

   retval = _atodbl(&dblval, str1);

   printf("Double value: %lf\n", dblval.x);
   printf("Return value: %d\n\n", retval);

   retval = _atoflt(&fltval, str1);
   printf("Float value: %f\n", fltval.f);
   printf("Return value: %d\n\n", retval);

   // A non-floating point value: returns 0.
   retval = _atoflt(&fltval, abc);
   printf("Float value: %f\n", fltval.f);
   printf("Return value: %d\n\n", retval);

   // Overflow.
   retval = _atoflt(&fltval, oflow);
   printf("Float value: %f\n", fltval.f);
   printf("Return value: %d\n\n", retval);

   return 0;
}

Double value: 3.141593
Return value: 0

Float value: 3.141593
Return value: 0

Float value: 0.000000
Return value: 0

Float value: inf
Return value: 3