It seems you hadn't linked the math library. Try -lm switch. For example "gcc prime.c -lm" Regards Rakesh > -----Original Message----- > From: Albert van Aardt [mailto:avanaardt@xxxxxxxxxxx] > Sent: Friday, September 26, 2003 8:50 AM > To: gcc-help@xxxxxxxxxxx > Subject: Newbie help please > > > I am trying to compile a simple C program: > > #include "stdio.h" > #include "math.h" > > int number; > > main() > { > printf("Which number do you wish to start the test with? "); > scanf("%d",&number); > printf("\n"); > printf("I'm starting with number %d\n",number); > if (number<1) number=1; > if (number==1) printf("1\n"); > if (number<=2) printf("2\n"); > if (!(number % 2)) number++; > if (number==1) number=3; > do > { > if (isprime(number)) printf("%d\n",number); > number+=2; > }while (1) ; > } > > isprime(int thenumber) > { > int isitprime=1,loop; > for(loop=3 ; (isitprime) && > (loop<(sqrt(thenumber)+1)) ; loop+=2) > isitprime = (thenumber % loop); > return(isitprime); > } > > > > > Compile it: > > gcc prime.c > > but then I get this error: > > > /tmp/ccdHcjqd.o(.text+0x128): In function `isprime': > : undefined reference to `sqrt' > collect2: ld returned 1 exit status > > > I have also tried some other programs, and all seem to give > this "sqrt" error. > Clearly I am doing something stupid, but surely GCC can > handle square roots? > > > Please advise! > > (RedHat 9) > > -- > > > Albert & Sue van Aardt > Whangarei > New Zealand > > Linux rules! >
