function [ y_out ] = laff_axpy( alpha, x, y )

% y = copy( x, y ) copies vector x into vector y
%   Vectors x and y can be a mixture of column and/or row vector.  In other
%   words, x and y can be n x 1 or 1 x n arrays.  However, one size must
%   equal 1 and the other size equal n.
%
%   The reason y is an input parameter is that the input y indicates
%   whether the output, y_out, is a column or row vector, and then also
%   indicates whether x must be transposed (e.g., if x is a row vector and
%   y is a column vector).

% Extract the row and column sizes of x and y
[ m_x, n_x ] = size( x );
[ m_y, n_y ] = size( y );

% Make sure x and y are (row or column) vectors of equal length
if ( m_x ~= 1 & n_x ~= 1 ) | ( m_y ~= 1 & n_y ~= 1 )
    y_out = 'FAILED';
    return
end
if ( m_x * n_x ~= m_y * n_y )
    y_out = 'FAILED';
    return
end
if ~isscalar( alpha )
    y_out = 'FAILED';
    return
end

if ( n_x == 1 )     % x is a column vector
    if ( n_y == 1 )     % y is a column vector
        % Copy the elements of x into the elements of y
        for i=1:m_x
            y( i,1 ) = alpha * x( i,1 ) + y( i,1 );
        end
    else     % y is a row vector
        % Copy the elements of x into the elements of y
        for i=1:m_x
            y( 1,i ) = alpha * x( i,1 ) + y( 1,i );
        end
    end
else    % x is a row vector
    if ( n_y == 1 )     % y is a column vector
        % Copy the elements of x into the elements of y
        for i=1:n_x
            y( i,1 ) = alpha * x( 1,i ) + y( i,1 );
        end
    else     % y is a row vector
        % Copy the elements of x into the elements of y
        for i=1:n_x
            y( 1,i ) = alpha * x( 1,i ) + y( 1,i );
        end
    end
end

% Return the updated y in y_out
y_out = y;

return
end