《DSP using MATLAB》示例 Example 6.11

% 
x = -7:7
y = OnesComplement(x, 4)

function [y] = OnesComplement(x, B);
	% Decimal equivalent of Sign-Magnitude format integer 
        % to b-bit Ones‘-Complement format conversion 
	% ----------------------------------------------------------
	% [y] = ladrfilt(x, B)
        %  x = integer between    -2^(b-1) < x < 2^(b-1)       (sign-magnitude)
	%  y = integer between           0 <= y <= 2^b-1       (1‘s-complement) 
	% 
        %
    if any((x <= -2^(B-1) | (x >= 2^(B-1))))
        error(‘Numbers must satisfy -2^(B-1) < x < 2^(B-1)‘)
    end
    s = sign(x);                  % sign of x (-1 if x<0,  0 if x=0, 1 if x>0)
    sb = (s < 0);                 % sign-bit  (0 if x>=0, 1 if x<0)
    y = (1-sb) .* x + sb .* bitcmp(abs(x), B);