Merge pull request #7 from JuliaMath/sb/export

Conditionally export/import symbols.

README.md

@@ -8,6 +8,8 @@
 
 Julia functions for computing prime numbers.
 
+## Usage
+
 At the moment, this repository just contains the following functions which have been duplicated from Base Julia:
 
     factor(n) -> Dict
@@ -50,4 +52,7 @@ true
 > Returns a prime sieve, as a `BitArray`, of the positive integers (from `lo`, if specified)
 up to `hi`. Useful when working with either primes or composite numbers.
 
-None of these are currently exported, so need to be explicitly imported before use.
+To avoid naming conflicts with Base, these are not exported for Julia version 0.4. In this case you will need to explicitly import the symbols:
+
+    using Primes
+    import Primes: isprime, primes, primesmask, factor

src/Primes.jl

@@ -1,6 +1,14 @@
 __precompile__()
 module Primes
 
+if VERSION >= v"0.5.0-dev+4340"
+    if isdefined(Base,:isprime)
+        import Base: isprime, primes, primesmask, factor
+    else
+        export isprime, primes, primesmask, factor
+    end
+end
+
 # Primes generating functions
 #     https://en.wikipedia.org/wiki/Sieve_of_Eratosthenes
 #     https://en.wikipedia.org/wiki/Wheel_factorization