How to fix Non-constant expression or empty matrix

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San 2012-7-8

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/43029-how-to-fix-non-constant-expression-or-empty-matrix

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Help me please.

There is any different between following codes?

Case 1:

    m_intrlvr = zeros(10,1);
    m_intrlvr(1) = 4;
    m_intrlvr(2) =7;
    m_intrlvr(3) =10;
    m_intrlvr(4) =3;
    m_intrlvr(5) =6;
    m_intrlvr(6) =9;
    m_intrlvr(7) =2;
    m_intrlvr(8) =5;
    m_intrlvr(9) =8;
    m_intrlvr(10) =1;        
    persistent hTBCode;
    if isempty(hTBCode )
        hTBCode  = comm.TurboEncoder('TrellisStructure', ...
            poly2trellis(4,[13 15], 13), 'InterleaverIndices', m_intrlvr);      
    end

Case 2:

    m_intrlvr = [4;7;10;3;6;9;2;5;8;1];
    persistent hTBCode;
    if isempty(hTBCode )
        hTBCode  = comm.TurboEncoder('TrellisStructure', ...
            poly2trellis(4,[13 15], 13), 'InterleaverIndices', m_intrlvr);      
    end

The first case it raise error: Non-constant expression or empty matrix. This expression must be constant because its value determines the size or class of some expression. Internal Error: This error occurred inside a MathWorks function.

P-code function 'pvparse.p' produced an error.

but the second one it is ok. anyone can help me where is my wrong?

(Re-opened)

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Walter Roberson 2012-7-8

在 MATLAB Online 中打开

Then I suspect it is trying to do code generation and that the code needs to conform to the Embedded MATLAB standards.

My (weak) knowledge is that m_intrlvr = zeros(10,1) should work for that situation. It would, however, not necessarily work if really the code was

numvals = 10;
m_intrlvr = zeros(numvals, 1);

Though it might in that particular case as it can see numvals as a constant. If the number of values was being passed through a signal then it would not work.

Which MATLAB version are you using? I have a vague memory of someone mentioning a bug in the automated code generation, a small number of releases ago.

San 2012-7-8