stdio.h to iostream?

[qwertyking]

Write your question here.
So i was doing the homework for my class, and I was stuck as always and asked my friend to help me with it. he wrote the code correctly...in stdio.h
I need it to be iostream, but I have no clue how to change it
Please help me
[code]
Put the code you need help with here.
#include<stdio.h>
#include<string.h>
#include<math.h>
bool isprime(int);
int countprime(int);
bool isprime(int n)
{
int i,j,k,f=0;
int d=sqrt(n);
for(i=2;i<=d;i++)
{
if(n%i==0)
{
f=1;
i=i+d;
}
}
if(f==1)
return false;
else
return true;

}
int countprime(int n)
{
int i,j,k,count=0;
for(i=2;i<=n;i++)
{
int f=0;
int d=sqrt(i);
for(j=2;j<=d;j++)
{
if(i%j==0)
{
f=1;
j=j+n;
}
}
if(f==0)
count++;

}
return count;
}
int main()
{

int i,j,n;
bool k;
printf("Enter an integer:\n");
scanf("%d",&n);
while(n>=0)
{
if(n>1)
{
k=isprime(n);
if(k)
printf("%d is a prime? true\n",n);
else
printf("%d is a prime? false\n",n);
j=countprime(n);
printf("Number of primes <= %d: %d\n",n,j);
}
else if(n==0)
{
printf("%d is a prime? false\n",n);
printf("Number of primes <= %d: %d\n",n,0);
}
else if(n==1)
{
printf("%d is a prime? false\n",n);
printf("Number of primes <= %d: %d\n",n,0);
}
printf("Enter another integer:\n");
scanf("%d",&n);
}
return 0;
}

[Zhuge]

Start here:
http://www.cplusplus.com/doc/tutorial/basic_io/

[qwertyking]

so the
printf = cout
scanf = cin
so if i change stdio.h to iostream

printf("%d is a prime? false\n",n);

cout << "%d is a prime? flase" << n << "\n";

printf("Number of primes <= %d: %d\n",n,0);

cout << "Number of primes <=%d: %d" << n << 0 << "\n";

is it correct?

Also,

for(j=2;j<=d;j++)

for(j=2;j<=d;j=j+1)

is it the same??

[giblit]

%X is used to replace with a variable so printf(%d is a prime? false\n",n); would be equal to cout << n << " is a prime? false" << std::endl;

Anyways I would suggest writing it in your own version and not just converting it from c to c++. Another thing to mention is that those prime functions are very slow and do unnecessary checks. I would suggest using a sieve. One of the easiest to implement is the sieve of eratosthenes http://en.wikipedia.org/wiki/Sieve_of_Eratosthenes

[18hRX9L8]

Very close. In C++ IO, there is no %anything... Instead, you must put the variable where the %something is. For example:

printf("%d is a prime? false\n",n);
std::cout << n << "is a prime? false\n";

printf("Number of primes <= %d: %d\n",n,0);
std::cout << "Number of primes <= " << n << ": " << 0;

printf("Somevar: %d, somevar1: %f, somevar2: %s\n\n", m, n, o);
std::cout << "Somevar: " << m << ", somevar1: " << n << ", somevar2: " << o << "\n\n";

[qwertyking]

what is

scanf("%d",&n);

so as you said there is no %something in c++

then like your example, it's gotta be

cin >> &n >> "\n"

i don't know what that &n is QQ

[qwertyking]

Also, I just checked the code and it is not compiling with visual studio 2012
can anyone check it and tell me what is wrong??

[long double main]

scanf("%d",&n); would be std::cin >> n; in C++.

[giblit]

Basically %d means you are inputting into an integer variable and &n is the address of n. So you will want to do cin >> n; also you are reading into the variable n. It would be hard to read into a newline.

If your homework is on functions, loops, input, output then your teacher should have taught you how to use cout and cin.

If not that is very odd and maybe you should take a look at this:
http://www.cplusplus.com/doc/tutorial/basic_io/

[qwertyking]

Thank you everyone I finally changed everything because of your help

Thank you so much fellows