ID Number: Q57244
5.10 6.00 6.00a 6.00ax 7.00 | 5.10 6.00 6.00a
MS-DOS | OS/2
Summary:
The gcvt() function returns an exponential number in the string even
if the number fits in the specified precision when the number is of
the form 0.0x, where x is any digit(s). Because of this behavior with
the gcvt() function, floating-point numbers cannot be converted to a
string.
More Information:
Another function that converts a floating-point number to a string is
fcvt(). Unfortunately, it does not do all the conversion for you
because it leaves out both the decimal point and the sign of the
number.
You can also use the sprintf() or printf() function with the "%lf"
format specifier to obtain the correct results. However, if you do not
want to use any printf() constructs, supporting code is needed to
completely convert the floating-point number to a string. The
following program shows one possible way this can be done, and the
printf() statements can be replaced by puts() statements:
Sample Code
-----------
#include <stdio.h>
#include <stdlib.h>
#include <malloc.h>
#include <string.h>
#define PRECISION 8
char *double_to_char (double) ;
char *temp2 ;
void main (void)
{
temp2 = double_to_char ((double) 0.0004567891) ;
printf ("temp = %s\n", temp2) ;
free (temp2) ;
temp2 = gcvt ((double) 0.0004567891, PRECISION, temp2) ;
printf ("temp = %s\n", temp2) ;
free (temp2) ;
temp2 = double_to_char ((double) 123.564) ;
printf ("temp = %s\n", temp2) ;
free (temp2) ;
temp2 = double_to_char ((double) -43.7864383846738) ;
printf ("temp = %s", temp2) ;
free (temp2) ;
}
/* Translates a double to an ASCIIZ string */
char *double_to_char (double number)
{
char *buffer,
*temp ;
int decimal_spot,
sign,
count,
current_location = 0 ;
temp = fcvt (number, PRECISION, &decimal_spot, &sign) ;
if (strlen (temp) > PRECISION)
buffer = (char *) malloc (strlen (temp) + 3) ;
else
buffer = (char *) malloc (PRECISION + 3) ;
if (buffer == NULL)
{
printf ("Memory allocating attempt has failed in"
"'double_to_char'\n") ;
exit (-1) ;
}
/* Add negative sign if required. */
if (sign)
buffer [current_location++] = '-' ;
/* Place decimal point in the correct location. */
if (decimal_spot > 0)
{
strncpy (&buffer [current_location], temp, decimal_spot) ;
buffer [decimal_spot + current_location] = '.' ;
strcpy (&buffer [decimal_spot + current_location + 1],
&temp [decimal_spot]) ;
}
else
{
buffer [current_location] = '.' ;
for(count = current_location; count<abs (decimal_spot); count++)
buffer [count + 1] = '0' ;
strcpy (&buffer [count + 1], temp) ;
}
return (buffer) ;
}
Additional reference words: 5.10 6.00 6.00a 6.00ax 7.00