Function: primes
Section: number_theoretical
C-Name: primes0
Prototype: G
Help: primes(n): returns the vector of the first n primes (integer), or the
 primes in interval n = [a,b].
Doc: creates a row vector whose components are the first $n$ prime numbers.
 (Returns the empty vector for $n \leq 0$.) A \typ{VEC} $n = [a,b]$ is also
 allowed, in which case the primes in $[a,b]$ are returned
 \bprog
 ? primes(10)     \\ the first 10 primes
 %1 = [2, 3, 5, 7, 11, 13, 17, 19, 23, 29]
 ? primes([0,29])  \\ the primes up to 29
 %2 = [2, 3, 5, 7, 11, 13, 17, 19, 23, 29]
 ? primes([15,30])
 %3 = [17, 19, 23, 29]
 @eprog