问个函数返回值的问题

HolySaint

1. function [genpoly,t] = rsgenpoly(N, K, varargin)
   
2. %RSGENPOLY  Generator polynomial of Reed-Solomon code.
   
3. %   GENPOLY = RSGENPOLY(N,K) returns the narrow-sense generator polynomial of a
   
4. %   Reed-Solomon code with codeword length N and message length K.  The codeword
   
5. %   length N must have the form 2^m-1 for some integer m between 3 and 16.  The
   
6. %   output GENPOLY is a Galois row vector that represents the coefficients of
   
7. %   the generator polynomial in order of descending powers.  The narrow-sense
   
8. %   generator polynomial is (X-alpha)*(X-alpha^2)*...*(X-alpha^(N-K)), where
   
9. %   alpha is a root of the default primitive polynomial for the field GF(N+1).
   
10. %
    
11. %   GENPOLY = RSGENPOLY(N,K,PRIM_POLY) is the same as the syntax above, except
    
12. %   that PRIM_POLY specifies the primitive polynomial for GF(N+1) that has alpha
    
13. %   as a root.  PRIM_POLY is an integer whose binary representation indicates
    
14. %   the coefficients of the primitive polynomial in order of descending powers.
    
15. %   To use the default primitive polynomial, set PRIM_POLY to [].
    
16. %
    
17. %   GENPOLY = RSGENPOLY(N,K,PRIM_POLY,B) returns the generator polynomial
    
18. %   (X-alpha^B)*(X-alpha^(B+1))*...*(X-alpha^(B+N-K-1)), where B is an integer
    
19. %   and alpha is a root of PRIM_POLY.
    
20. %
    
21. %   [GENPOLY,T] = RSGENPOLY(...) returns T, the error-correction capability of
    
22. %   the code.
    
23. %
    
24. %   Examples:
    
25. %      g  = rsgenpoly(7,3)       % Narrow-sense generator polynomial
    
26. %      g2 = rsgenpoly(7,3,13)    % Narrow-sense generator polynomial,
    
27. %                                %   with respect to primitive polynomial
    
28. %                                %   D^3+D^2+1
    
29. %      g3 = rsgenpoly(7,3,[],4)  % Use b=4
    
30. %
    
31. %   See also GF, RSENC, RSDEC.
    
32. 
    
33. 
    
34. 
    
35. %    Copyright 1996-2007 The MathWorks, Inc.
    
36. %    $Revision: 1.4.4.2 $  $Date: 2007/09/14 15:57:43 $
    
37. 
    
38. 
    
39. % Initial checks
    
40. error(nargchk(2,4,nargin,'struct'));
    
41. 
    
42. % Number of optional input arguments
    
43. nvarargin = nargin - 2;
    
44. 
    
45. % Error-correcting capability
    
46. t = floor((N-K)/2);
    
47. t2 = N-K;
    
48. m = log2(N+1);
    
49. def_primpoly = 1;
    
50. b = 1;  % Default : narrow-sense
    
51. 
    
52. if any([~isscalar(N) | ~isscalar(K) | floor(N)~=N | floor(K)~=K])
    
53.     error('comm:rsgenpoly:InvalidNK','N and K must be positive scalar integers.');
    
54. end
    
55. 
    
56. if t2<1
    
57.     error('comm:rsgenpoly:NLessThanK','N must be larger than K.');
    
58. end
    
59. 
    
60. if m~=floor(m) | m<3 | m>16
    
61.   error('comm:rsgenpoly:InvalidN','N must equal 2^m-1 for some integer m between 3 and 16.')
    
62. end
    
63. 
    
64. if ~isempty(varargin)
    
65. 
    
66.     prim_poly = varargin{1};
    
67. 
    
68.     % Check prim_poly
    
69.     if isempty(prim_poly)
    
70.         if ~isnumeric(prim_poly)
    
71.             error('comm:rsgenpoly:InvalidDefaultPrim_Poly','To use the default PRIM_POLY, it must be marked by [].');
    
72.         end
    
73.     else
    
74.         if ~isscalar(prim_poly)
    
75.             error('comm:rsgenpoly:Prim_PolyNotScalar','PRIM_POLY must be a scalar integer.');
    
76.         end
    
77.         % ZZZ add isprimitive once it's available
    
78.         def_primpoly = 0;
    
79.     end
    
80. 
    
81.     if nvarargin==2
    
82.         b = varargin{2};
    
83.         if ~isscalar(b) | floor(b)~=b
    
84.             error('comm:rsgenpoly:BNotAnInt','B must be an integer scalar.');
    
85.         end
    
86.     end
    
87. end
    
88. 
    
89. % Alpha is the primitive element of this GF(2^m) field
    
90. if def_primpoly == 1
    
91.     alpha = gf(2,m);
    
92. else
    
93.     alpha = gf(2,m,prim_poly);
    
94. end
    
95. 
    
96. 
    
97. genpoly = 1;
    
98. for k=mod(b+[0:t2-1],N)
    
99.     evalc('genpoly = conv(genpoly,[1 alpha.^(k)]);');
    
100. end
     
101. 
     

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大家帮忙看看
我想获得这个返回值，即将他赋给一个变量POLY
rsgenpoly(31,25)
POLY = [1          17          26          30          27          30          24];

试了改了一下没有成功
多谢啊

HolySaint

>> rsgenpoly(31,25)

ans = GF(2^5) array. Primitive polynomial = D^5+D^2+1 (37 decimal)

Array elements =

           1          17          26          30          27          30          24

默认返回这个

HolySaint

1. >> POLY=rsgenpoly(31,25);
   
2. >> POLY
   
3. 
   
4. POLY = GF(2^5) array. Primitive polynomial = D^5+D^2+1 (37 decimal)
   
5. 
   
6. Array elements =
   
7. 
   
8.            1          17          26          30          27          30          24
   
9. 
   
10. >> POLY(1)
    
11. 
    
12. ans = GF(2^5) array. Primitive polynomial = D^5+D^2+1 (37 decimal)
    
13. 
    
14. Array elements =
    
15. 
    
16.            1
    
17. 
    
18. >> POLY(1)+POLY(2)
    
19. 
    
20. ans = GF(2^5) array. Primitive polynomial = D^5+D^2+1 (37 decimal)
    
21. 
    
22. Array elements =
    
23. 
    
24.           16

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怎么把POLY变成普通的向量呢？

Happy99

专业不懂, 稍微搜下help, 没试成
建议考量简化下

HolySaint

回复 4 # Happy99 的帖子

不是太懂，所以说的也不是太明白哈，我在研究一下
就是把poly变量变成普通的变量，你看那个加法就知道了

qibbxxt

只需要在函数的末尾加上

1. genpoly=genpoly.x;

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因为gf是个结构体，可以用

1. open gf

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查看代码
运行的结果：

1. >> pp=rsgenpoly(31,25)
   
2. 
   
3. pp =
   
4. 
   
5.            1          17          26          30          27          30          24

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HolySaint

回复 6 # qibbxxt 的帖子

多谢哈，成功了

Happy99

建议不要修改源程序,直接使用POLY=rsgenpoly(31,25); pp=POLY.x即可

昨晚第一时间亦是朝这个方向! 但没试对fieldname, 又一时没找到查询函数(应用fieldnames, 原少个s字)
原来那些值是'x'!
请教gf class的cmd win显示好像与结构体不同, 结构体直接就有fieldname显示!?

HolySaint

回复 8 # Happy99 的帖子

恩，我也是在我的程序里直接提取的，没有改gf域的那个函数，多谢哈～～