_atodbl, _atodbl_l, _atoldbl, _atoldbl_l, _atoflt, _atoflt_l

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.

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

See also

Data Conversion
Floating-Point Support
Locale
atof, _atof_l, _wtof, _wtof_l