Short version: means the expression can be seen as 1D vector. Long version: means that one can access the coefficients of this expression by coeff(int), and coeffRef(int) in the case of a lvalue expression. These indexbased access methods are guaranteed to not have to do any runtime computation of a (row, col)pair from the index, so that it is guaranteed that whenever it is available, indexbased access is at least as fast as (row,col)based access. Expressions for which that isn't possible don't have the LinearAccessBit. If both PacketAccessBit and LinearAccessBit are set, then the packets of this expression can be accessed by packet(int), and writePacket(int) in the case of a lvalue expression. Typically, all vector expressions have the LinearAccessBit, but there is one exception: Product expressions don't have it, because it would be troublesome for vectorization, even when the Product is a vector expression. Thus, vector Product expressions allow indexbased coefficient access but not indexbased packet access, so they don't have the LinearAccessBit. Definition at line 133 of file Constants.h. Referenced by MapBase< Map< MatrixType, PacketAccess > >::coeff(), and MapBase< Map< MatrixType, PacketAccess > >::coeffRef().
