Adding missing header (Issue 565)

stan/math/rev/core/build_double_array.hpp

@@ -2,6 +2,7 @@
 #define STAN_MATH_REV_CORE_BUILD_DOUBLE_ARRAY_HPP
 
 #include <stan/math/rev/core/vari.hpp>
+#include <algorithm>
 #include <limits>
 
 namespace stan {
@@ -32,8 +33,7 @@ inline double* build_double_array(vari** array, int size) {
  * @return Copy of input array
  */
 inline double* build_double_array(const double* array, int size) {
-  double* copy
-      = ChainableStack::instance().memalloc_.alloc_array<double>(size);
+  double* copy = ChainableStack::instance().memalloc_.alloc_array<double>(size);
 
   std::copy(array, array + size, copy);