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Re: isPrime() 17 Years Ago by Narue … it hard to believe that you can write IsPrime but not the main driver to print the… [0..100). I'm guessing you were given IsPrime and told to write main, which means [B… is loop from 0 to 100 and call IsPrime on the current number. If it returns true…( int i = 0; i < 100; i++ ) { if ( IsPrime ( i ) ) cout<< i <<" is prime… Re: isPrime() 17 Years Ago by JRM … I find it hard to believe that you can write IsPrime but not the main driver to print the primes in… the range [0..100). I'm guessing you were given IsPrime and told to write main, which means ***you've*** come… Re: isPrime() 14 Years Ago by hvengel An even more efficient and generalized isPrime() function. [CODE]bool isPrime (unsigned int number) { if (number > 3) { if (number % 2 == … Re: isPrime() 14 Years Ago by hvengel …} sieveValue++; } sieve.push_back(wheelFactor + 1); sieveFull = true; } bool isPrime (unsigned int candidatePrime) { if (!sieveFull) fillSieve(); int fp = 0; while…; } [/CODE] Here is a wheel factorization version of isPrime. This uses a small wheel factoring sieve based on the… isPrime() 17 Years Ago by forumposters I need to write a main() function, that loops over a bunch of numbers from 0 to 100, calls another function called isPrime() for each of them, and print out the numbers that are prime. I'm new to C++ and any help would be appreciated. Re: isPrime() 17 Years Ago by sillyboy What narue said applies. But I'll help you a little: isPrime(int x) Re: isPrime() 17 Years Ago by forumposters Here's what I've come up with so far: [code] #include <iostream> bool IsPrime(int num) { if(num == 0) return true; num = abs(num); for(int i = 2; i <= sqrt(num); i++) if(num % i == 0) return false; return true; }[/code] Re: isPrime() 14 Years Ago by soeja This is more efficient. #include <iostream> bool IsPrime(int num) { if(num == 0) return true; num = abs(num); if(num % 2 == 0) return true; for(int i = 3; i <= sqrt(num); i+=2) if(num % i == 0) return false; return true; } Re: isPrime() 14 Years Ago by soeja [CODE]#include <iostream> bool IsPrime(int num) { if(num == 0) return true; num = abs(num); if(num % 2 == 0) return true; for(int i = 3; i <= sqrt(num); i+=2) if(num % i == 0) return false; return true; }[/CODE] Re: isPrime() 14 Years Ago by parameshyss Hi Soeja, This is more efficient.. and for 4 , 6 , 8(i.e., even no) .. ur code snippet will give wrong ans.. [code=c] #include <iostream> bool IsPrime (int num) { if ( 2 == num ) return true ; int l = sqrt(num) ; for(int i = 3; i <= l; i+=2) if ( 0 == ( num % i ) ) return false; return true; } [/code] Re: IsPrime.cpp 15 Years Ago by csurfer … Hiroshe): [B]1>[/B] [QUOTE]if (IsPrime(num)==(true))[B][COLOR="Red"];[/COLOR][/B]… don't do redundant work as in [B]IsPrime(num)==(true)[/B] the following is enough: […code=c] if (IsPrime(num)) //No semicolon and a return of 1… [/code] [B]2>[/B] And in your IsPrime function with this line : [code=c]for (i=3… IsPrime.cpp 15 Years Ago by ndfi54 …quot;random.h" #include <math.h> bool IsPrime(int num); int main() { int num; num=2; printf(&…num); for (num=3;num<=100;num+=2) { if (IsPrime(num)==(true)); { printf("%d\n", num); } } } …bool IsPrime(int num) { int i; double limit; if (num<=1… Re: isPrime() 17 Years Ago by Narue >I'm new to C++ and any help would be appreciated. At least start trying to solve your problem before asking for help. It makes us like you more and ignore you less. Re: isPrime() 17 Years Ago by WaltP You've been around over a year and haven't read [url=http://www.daniweb.com/techtalkforums/faq.php?faq=daniweb_policies]the Rules[/url] yet? You also need to [url=http://www.daniweb.com/techtalkforums/thread78223.html]read this[/url]. It will explain that you need to tell us what problem you are having so we don't have to guess -- among other … Re: isPrime() 14 Years Ago by parameshyss Gud work hvengel.. :) Re: isPrime() 14 Years Ago by StuXYZ I am surprised reading this, I would have thought most of you knew the +2,+4 rule -- but it hasn't come up, just the old +2 rule. Assuming that you are not going to use the memory that the typical sieve methods use, or the complexity of the more you can extend the idea that you increment the test by +2 to +2,+4 as below. [code=C++] bool … Re: isPrime() 14 Years Ago by pseudorandom21 I think a sieve that uses a bit of memory is way better than using that much CPU time, you can generate millions of primes in a few seconds using a sieve. Re: isPrime() 14 Years Ago by pseudorandom21 [url]http://en.wikipedia.org/wiki/Primality_test[/url] You might also look into the sieve of eratosthenes, and other algorithms for generating primes. [url]http://en.wikipedia.org/wiki/Sieve_of_Eratosthenes[/url] There are links to other algorithms at the bottom, such as the sieve of sundaram, etc. Re: isPrime() 14 Years Ago by yashsaxena prime number program :) Still remember the initial days of C & CPP programming Language. :P :) Re: isprime function (Python) 10 Years Ago by TrustyTony Interesting HiHe, but I do not know if it is too biased to use only one number as case. Both isprime2 and isprime 3 seem to run more than my own isprime adapted as optimized from Project Euler (found in other prime tread recently posted to) Tony Re: isprime function (Python) 10 Years Ago by HiHe … little timing experiment: ''' timeit_isprime.py check the speed of three isprime functions ''' import timeit import sys print(sys.version) def isprime2… C4715: 'isPrime' : not all control paths return a value 17 Years Ago by Yaka …running how ever it gives this warning....C4715: 'isPrime' : not all control paths return a value....i…; "is a prime number\n"; } if (isPrime(number)==false) { cout << "\n"…Invalid number entered\n"); exit(1); } } int isPrime(int number) { int count=0,count1; for(count1=2;… Re: C4715: 'isPrime' : not all control paths return a value 17 Years Ago by Yaka … the warning off. and yea i made the int isprime ,,, a bool isprime. thanks. but still i dont know how to fix… Re: Help creating an isPrime function 13 Years Ago by mrnutty …[code] #include <iostream> using namespace std; bool isPrime(int number){ bool isPrimeNumber = false; //do logic here return …lt;< "Is 97 prime: " << isPrime(97) << endl; //should be true cout <<… << "Is 27 prime: " << isPrime(27) << endl; //should be false return 0; } … Re: Help creating an isPrime function 13 Years Ago by mrnutty …[code] #include <iostream> using namespace std; bool isPrime(int number){ bool isPrimeNumber = false; //do logic here return …lt;< "Is 97 prime: " << isPrime(97) << endl; //should be true cout <<… << "Is 27 prime: " << isPrime(27) << endl; //should be false return 0; } … Recursive isPrime function in python 11 Years Ago by birinci2012 def isPrime(num,div=2): if(num==div): return True elif(num % div == 0): return False else: return isPrime(num,div+1) Re: Help creating an isPrime function 13 Years Ago by rigoalhn …;iostream> #include <iomanip> using namespace std; bool isPrime(int number){ int remainder; bool isPrimeNumber = false; cout<<…; boolalpha << "Is 5 prime : " << isPrime(number) << endl; system("pause"); return 0… Re: Recursive isPrime function in python 11 Years Ago by Gribouillis Probably the worst `isPrime()` function I've ever seen. If num is above 1000000, … Help creating an isPrime function 13 Years Ago by rigoalhn … helped me. I need a write a boolean function named IsPrime that takes and integer as argument and returns true if… Timing five isprime functions (Python) 10 Years Ago by vegaseat Just trying to find out which of these five isprime functions is the fastest.