I have a prime number calculator program that uses type casting. The type casting occurs in my "prime_calculator" function, under "Discard remaining composite numbers".
If I run it without type casting it, I get an error msg "conversion from double to unsigned long; possible loss of data".
I was just wondering where/what is the "double"?
mw
Code:#include<stdio.h> #include<stdlib.h> #include<math.h> #include<malloc.h> /* This program calculates prime numbers using the Eratosthenes Sieve algorithm. It will find the prime numbers between 2 & "max". It overwrites the prime numbers to the file "prime_numbers.txt" in the same folder. Definitions: 1) Prime Number: a number with only 2 divisibles (itself & 1); the number "1" is not considered a prime number in this program 2) Composite Number: a number with more than 2 divisibles Variable key: discard = this is used to calculate composite numbers count = a variable I use to count with prime[max] = a pointer array that stores all of the numbers in the "max" range max = the maximum range of prime numbers to calculate highest = input from the user that is passed to "max" An in-depth explanation of the Eratosthenes Sieve can be found on the internet. */ //prototypes void start (void); void prime_calculator (unsigned long max); int main (void) { start (); return 0; } void start (void) { unsigned long highest; do { //input from user printf ("\nType '0' to quit."); printf ("\n\nPlease specify a max range to calculate prime numbers (up to 9000011).\n"); scanf ("%d", &highest); //check input from user if (highest < 0 || highest == 1 || highest > 9000011) { printf ("\n(Setting max range to 100)\n\n"); highest = 100; } //if user doesn't enter zero, call prime_calculator if (highest != 0) { prime_calculator (highest); } } while (highest != 0); } void prime_calculator (unsigned long max) { unsigned long discard; unsigned long count; //Open & overwrite file for output FILE *fp = fopen ("prime_numbers.txt", "w"); //Initialize the array int *prime = malloc ((max+1)*sizeof(*prime)); if (!prime) { puts ("\n\nERROR! Not enough Memory!\n\n"); exit (1); } //initialize prime[max] for (count = 0; count <= max; count++) { prime[count] = 1; } count = 0; printf ("\nFinished initializing array."); //Discard even composite numbers for (discard = 4; discard <= max; discard = discard + 2) { prime[discard] = 0; } discard = 0; printf ("\n\nFinished even discards."); //Discard remaining composite numbers count = 3; do { for (discard = (int) pow(count,2); discard <= max; discard = discard + count * 2) { if (prime[discard] > 0) { prime[discard] = 0; } } count++; } while (pow(count,2) <= max); count = 0; discard = 0; printf ("\n\nFinished all other discards."); //Output printf ("\n\nPrime Numbers between 2 and %d...\n", max); for (count = 2; count <= max; count++) { if (prime[count] == 1) { printf ("%d ", count); fprintf (fp,"\t%d", count); } } count = 0; fclose (fp); free (prime); printf ("\n\n"); }
Originally Posted by Lionmane
