《DSP using MATLAB》示例Example 6.12

上代码：

% 
x = -8:7
y = TwosComplement(x, 4)

y = dec2bin(y, 4);
disp(sprintf('%s', [y'; char(ones(1, 16) * 32)]))

　　函数TwosComplement代码：

function [y] = TwosComplement(x, B);
	% Decimal equivalent of Sign-Magnitude format integer 
    % to B-bit Twos'-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       (2'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) + 1);  % y = (1-sb) .* x + sb .* (2^B + x)

　　运行结果：