CODEWITHSUNDEEP
c++matlab
suranga
suranga

Reputation: 228

Matlab coder build error when trying to access structures

I have a nested structure with some fields labeled as L1, L2 etc. I try to access a substructure within the structure using the following code.

lfield = lfidcalc(le);
substruct = bmstruct.(lfield);

Since le changes its value in every iteration, lfield also changes its value from L1 to L9.

However, when I try to build this code to generate a C++ executable, I get the following error.

Non-constant expression or empty matrix. This expression must be constant because its value determines the size or class of some expression. In this context, the value of the string must be known.

Can anybody please try to help me sort out this problem?

Upvotes: 1

Views: 931

Answers (2)

Sam Roberts
Sam Roberts

Reputation: 24127

I'm not sure exactly what's causing the error message you're seeing, but in any case MATLAB Coder does not support accessing the fields of a structure using dynamic field names.

Perhaps that is the direct cause of what you're seeing, perhaps not: but in either case you have a problem.

Upvotes: 1

Martijn Pot
Martijn Pot

Reputation: 86

Not all correct matlab code can be converted to C/C++. Especially this kind of (very handy) code. Have you put '%#eml' on the second line of your function? It indicates that you will generate code. From matlab website: " We use the %#eml directive to turn on the MATLAB M-Lint code analyzer and check the function code for errors and recommend corrections."

Upvotes: 0

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