Shortest Prime Checker

Question

Who can write a shorter prime checking function in any language?
Whitespace characters don't count.
You do not have to care about efficiency.

Your function has to put out the correct answer in a program like:
if isPrime(x):
print (x, "is a prime")

My function:
def isPrime (n):
i=b=2 # 5
while i < n: # 9
b*=n%i # 6
i+=1 # 4
return b # 7
# sum: 31

Answer 1

It's not the shortest (C++ never is), but here's a short prime function with 97 chars in C++11.

bool isprime(int i){
static bool(*p)(int,int)=[](int i,int n)->bool{return i<3?1:i^n?i%n&&p(i,n+1):1;};
return p(i, 2);
}

Technically, only the lambda line is needed, so you can argue it's really in 82 characters.