Prime

This is a discussion on Prime within the C Programming forums, part of the General Programming Boards category; Computing teacher gave me homework to make a program which checks if a number is prime i wrote this: Code: ...

  1. #1
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    Prime

    Computing teacher gave me homework to make a program which checks if a number is prime i wrote this:
    Code:
    int asal(int a,int b){
    	if(b=1){return 2;}
    	else if(a%b!=0){return asal(a,b-1);}
    	else if(a%b==0){return 1;}}
    
    int main(){
    	if(asal(27,26)==2){printf(" is a prime");}
    	if(asal(27,26)==1){printf(" isn't a prime");}
    	getchar();
    	return 0;}
    it returns "its a prime" where is the problem????

  2. #2
    Kernel hacker
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    Try adding a printf() to the beginning of asal() to show the value of a and b respectively.

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  3. #3
    ATH0 quzah's Avatar
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    Why does your function that checks for prime numbers require two inputs? That's just odd.


    Quzah.
    Hope is the first step on the road to disappointment.

  4. #4
    Captain Crash brewbuck's Avatar
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    Uh, your function returns either 1 or 2, both of which mean "true". Perhaps use 0 for false.
    Code:
    //try
    //{
    	if (a) do { f( b); } while(1);
    	else   do { f(!b); } while(1);
    //}

  5. #5
    spurious conceit MK27's Avatar
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    Nope. The problem is just "if (b==1)"

    Also I guess it need not be called twice...hmm.
    C programming resources:
    GNU C Function and Macro Index -- glibc reference manual
    The C Book -- nice online learner guide
    Current ISO draft standard
    CCAN -- new CPAN like open source library repository
    3 (different) GNU debugger tutorials: #1 -- #2 -- #3
    cpwiki -- our wiki on sourceforge

  6. #6
    Registered User slingerland3g's Avatar
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    Another suggestion would be to work off existing code that specializes in figuring out/calculating prime numbers which will be the openssl source code package. If you are fond at reviewing source code this would be a good place to seek out how efficient code is written. A great learning tool IMHO.

  7. #7
    ATH0 quzah's Avatar
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    It makes more sense to just type "prime" in the search box here, than it does to sort through the source code for openssl...


    Quzah.
    Hope is the first step on the road to disappointment.

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