How do I define a structure that has an element which is an array?

2012 12 6
4 个回答
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1 个投票

How do I define a structure that has an element which is an array and for which there are sub elements. I have composed a simple example below of what I want to do along with a failed attempt at the needed assert statements.
function y = payroll(personnel)
%#codegen
% Specify the class of the input as struct.
assert(isstruct(personnel));
% Specify the class and size of the fields r and i
% in the order in which you defined them.
assert(isa(personnel.num_employees,'int32'));
assert(isa(personnel.employee,'int32'));
assert(all(size(personnel.employee) == [5 1]));
assert(isa(personnel.employee(1).salary,'int32'));
for i = personnel.num_employees
total_payroll = total_payroll + personnel.name(i).salary;
end
y = total_payroll;
end

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Arnab De
Arnab De 2012-12-7
Do you just want to run the MATLAB code or do you want to generate C code from it?
Wayne Prather
Wayne Prather 2012-12-7
My purpose is to generate C code using Matlab Coder. I get an error related to my failure to properly define the employee element of my structure since it is an array and has a sub element uder it.

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Fred Smith
Fred Smith 2012-12-7

1 个投票

This line seems wrong:
assert(isa(personnel.employee,'int32'));
In your code employee is supposed to be a struct with sub-field name and salary? Once you make it a struct, you then also need to set its class and size of the fields name and salary.
-Fred

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Wayne Prather
Wayne Prather 2012-12-7
It finally works. Apparently you have to define the arrayed sub elements in the same way that you define the main structure. The following Matlab code works and succesfully produces the C++ code that follows.
Matlab code:
function y = payroll(personnel)
%#codegen
% Specify the class of the input as struct.
assert(isstruct(personnel));
% Specify the class and size of the fields r and i
% in the order in which you defined them.
assert(isa(personnel.num_employees,'int32'));
assert(isstruct(personnel.employee));
assert(all(size(personnel.employee) == [5 1]));
assert(isa(personnel.employee(1).salary,'double'));
total_payroll = 0;
for i = 1 : personnel.num_employees
total_payroll = total_payroll + personnel.employee(i).salary;
end
y = total_payroll;
end
Matlab Coder produced C++ code:
real_T payroll(const b_struct_T personnel)
{
real_T y;
int32_T i;
y = 0.0;
for (i = 1; i <= personnel.num_employees; i++) {
y += personnel.employee[i - 1].salary;
}
return y;
}

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更多回答（3 个）

John Petersen
John Petersen 2012-12-6
编辑：John Petersen 2012-12-6

0 个投票

1. Find out which assertion fails. The code looks fine.
2. Replace the 'for' loop with
y = sum([personnel.name.salary]);
Jan
Jan 2012-12-7

0 个投票

This will crash, if the personnel.employee has more than 2 dimensions:
all(size(personnel.employee) == [5 1])
Better:
isequal(size(personnel.employee), [5 1])
Sean de Wolski
Sean de Wolski 2012-12-7

0 个投票

total_payroll = total_payroll + personnel.name(i).salary;
total_payroll is never defined before being used for the first time!

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Wayne Prather
Wayne Prather 2012-12-7
Thanks, you are correct. I forgot to initialize it. The code is just a made up simplistic example that addresses the problem I am having in my real code in regards to defining a structure with elements which are arrays for the C++ code generation.

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