Mega Code Archive
Convert one or more floating-point values into a single string
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/*
Beginning C, Third Edition
By Ivor Horton
ISBN: 1-59059-253-0
Published: Apr 2004
Publisher: apress
*/
#include <stdio.h>
#include <stdlib.h>
#include <stdarg.h>
#include <string.h>
char* to_string(int count, double first, ...); /* Converts doubles to a string separated by commas */
char* fp_to_str(double x); /* Converts x to a string */
char* int_to_str(int n); /* Converts n to a string */
void main()
{
char *str = NULL; /* Pointer to the string of values */
double values[] = { 1.245, -3.5, 6.758, 33.399, -1.02 };
str = to_string(sizeof values/sizeof(double), values[0], values[1], values[2], values[3], values[4]);
printf("The string of values is:\n%s\n", str);
free(str); /* Free memory for string */
}
/************
* Function to convert one or more floating-point values to a *
* string with the values separated by commas. *
* This function allocates memory that must be freed by the caller *
************/
char* to_string(int count, double first, ...)
{
va_list parg = NULL; /* Pointer to variable argument */
char* str = NULL; /* Pointer to the joined strings */
char *temp = NULL; /* Temporary string pointer */
char *value_str = 0; /* Pointer to a value string */
const char *separator = ","; /* Separator in values string */
size_t separator_length = 0; /* Length of separator string */
size_t length = 0; /* Length of a string */
int i = 0; /* Loop counter */
separator_length = strlen(separator);
va_start(parg,first); /* Initialize argument pointer */
str = fp_to_str(first); /* convert the first value */
/* Get the remaining arguments, convert them and append to the string */
while(--count>0)
{
value_str = fp_to_str(va_arg(parg, double)); /* Get next argument */
length = strlen(str) + strlen(value_str) + separator_length +1;
temp = (char*)malloc(length); /* Allocate space for string with argument added */
strcpy(temp, str); /* Copy the old string */
free(str); /* Release old memory */
str = temp; /* Store new memory address */
temp = NULL; /* Reset pointer */
strcat(str,separator); /* Append separator */
strcat(str,value_str); /* Append value string */
free(value_str); /* Release value string memory */
}
va_end(parg); /* Clean up arg pointer */
return str;
}
/********************
* Converts the floating-point argument to a string. *
* Result is with two decimal places. *
* Memory is allocated to hold the string and must be freed by the caller. *
********************/
char* fp_to_str(double x)
{
char *str = NULL; /* Pointer to string representation */
char *integral = NULL; /* Pointer to integral part as string */
char *fraction = NULL; /* Pointer to fractional part as string */
size_t length = 0; /* Total string length required */
integral = int_to_str((int)x); /* Get integral part as a string with a sign */
/* Make x positive */
if(x<0)
x = -x;
/* Get fractional part as a string */
fraction = int_to_str((int)(100.0*(x+0.005-(int)x)));
length = strlen(integral)+strlen(fraction)+2; /* Total length including point and terminator */
/* Fraction must be two digits so allow for it */
if(strlen(fraction)<2)
++length;
str = (char*)malloc(length); /* Allocate memory for total */
strcpy(str, integral); /* Copy the integral part */
strcat(str, "."); /* Append decimal point */
if(strlen(fraction)<2) /* If fraction less than two digits */
strcat(str,"0"); /* Append leading zero */
strcat(str, fraction); /* Append fractional part */
/* Free up memory for parts as strings */
free(integral);
free(fraction);
return str;
}
/********************
* Converts the integer argument to a string. *
* Memory is allocated to hold the string and must be freed by the caller. *
********************/
char* int_to_str(int n)
{
char *str = NULL; /* pointer to the string */
int length = 1; /* Number of characters in string(at least 1 for terminator */
int temp = 0;
int sign = 1; /* Indicates sign of n */
/* Check for negative value */
if(n<0)
{
sign = -1;
n = -n;
++length; /* For the minus character */
}
/* Increment length by number of digits in n */
temp = n;
do
{
++length;
}
while((temp /= 10)>0);
str = (char*)malloc(length); /* Allocate space required */
if(sign<0) /* If it was negative */
str[0] = '-'; /* Insert the minus sign */
str[--length] = '\0'; /* Add the terminator to the end */
/* Add the digits starting from the end */
do
{
str[--length] = '0'+n%10;
}while((n /= 10) > 0);
return str;
}
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