`_ecvt`

Άρθρο
12/02/2022

Converts a double number to a string. A more secure version of this function is available; see _ecvt_s.

Syntax

char *_ecvt(
   double value,
   int count,
   int *dec,
   int *sign
);

Parameters

value
Number to be converted.

count
Number of digits stored.

dec
Stored decimal-point position.

sign
Sign of the converted number.

Return value

_ecvt returns a pointer to the string of digits; NULL if an error occurred.

Remarks

The _ecvt function converts a floating-point number to a character string. The value parameter is the floating-point number to be converted. This function stores up to count digits of value as a string and appends a null character ('\0'). If the number of digits in value exceeds count, the low-order digit is rounded. If there are fewer than count digits, the string is padded with zeros.

The total number of digits returned by _ecvt won't exceed _CVTBUFSIZE.

Only digits are stored in the string. The position of the decimal point and the sign of value can be obtained from dec and sign after the call. The dec parameter points to an integer value giving the position of the decimal point with respect to the beginning of the string. A 0 or negative integer value indicates that the decimal point lies to the left of the first digit. The sign parameter points to an integer that indicates the sign of the converted number. If the integer value is 0, the number is positive. Otherwise, the number is negative.

The difference between _ecvt and _fcvt is in the interpretation of the count parameter. _ecvt interprets count as the total number of digits in the output string, whereas _fcvt interprets count as the number of digits after the decimal point.

_ecvt and _fcvt use a single statically allocated buffer for the conversion. Each call to one of these routines destroys the result of the previous call.

This function validates its parameters. If dec or sign is NULL, or count is 0, the invalid parameter handler is invoked, as described in Parameter validation. If execution is allowed to continue, errno is set to EINVAL, and NULL is returned.

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

Requirements

Function	Required header
`_ecvt`	<stdlib.h>

For more compatibility information, see Compatibility.

Example

// crt_ecvt.c
// compile with: /W3
// This program uses _ecvt to convert a
// floating-point number to a character string.

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

int main( void )
{
   int     decimal,   sign;
   char    *buffer;
   int     precision = 10;
   double  source = 3.1415926535;

   buffer = _ecvt( source, precision, &decimal, &sign ); // C4996
   // Note: _ecvt is deprecated; consider using _ecvt_s instead
   printf( "source: %2.10f   buffer: '%s'  decimal: %d  sign: %d\n",
           source, buffer, decimal, sign );
}

source: 3.1415926535   buffer: '3141592654'  decimal: 1  sign: 0

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