C Programming Code Examples C > Conversions Code Examples Convert one or more floating-point values into a single string Convert one or more floating-point values into a single string #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; }
