The advantage is to avoid setting the include path of the compiler.
for example, in array-impl.h, change <> to "filename"
#include "blitz.h"
#include "memblock.h"
#include "range.h"
#include "tinyvec2.h"
#include "tvecglobs.h"
#include "indexexpr.h"
#include "array/slice.h" // Subarrays and slicing
#include "array/map.h" // Tensor index notation
#include "array/multi.h" // Multicomponent arrays
#include "array/domain.h" // RectDomain class
#include "array/storage.h" // GeneralArrayStorage