Write a function AddShift that takes an input Shift and adds it to the elements of a vector. The vector consists of the square of the first 10 natural numbers. AddShift generates this vector.

function y = AddShift(Shift) %#codegen
y = (1:10).^2+Shift;

Generate code for AddShift using the codegen command. Open the Code Generation Report.

codegen -config:lib -launchreport AddShift -args 0

The code generator produces code for creating the vector. It adds Shift to each element of the vector during vector creation. The definition of AddShift in generated code looks as follows:

void AddShift(double Shift, double y[10])
{
  int k;
  for (k = 0; k < 10; k++) {
    y[k] = (double)((1 + k) * (1 + k)) + Shift;
  }
}

Replace the expression (1:10).^2 with coder.const((1:10).^2), and then generate code for AddShift again using the codegen command. Open the Code Generation Report.

codegen -config:lib -launchreport AddShift -args 0

The code generator creates the vector containing the squares of the first 10 natural numbers. In the generated code, it adds Shift to each element of this vector. The definition of AddShift in generated code looks as follows:

void AddShift(double Shift, double y[10])
{
  int i;
  static const signed char iv[10] = { 1, 4, 9, 16, 25, 36, 
                                 49, 64, 81, 100 };

  for (i = 0; i < 10; i++) {
    y[i] = (double)iv[i] + Shift;
  }
}

Write a function getsine that takes an input index and returns the element referred to by index from a lookup table of sines. The function getsine creates the lookup table using another function gettable.

function y = getsine(index) %#codegen
  assert(isa(index, 'int32'));
  persistent tbl;
  if isempty(tbl)
           tbl = gettable(1024);
  end
  y = tbl(index);

function y = gettable(n)
      y = zeros(1,n);
      for i = 1:n
         y(i) = sin((i-1)/(2*pi*n));
      end

Generate code for getsine using an argument of type int32. Open the Code Generation Report.

codegen -config:lib -launchreport getsine -args int32(0)

The generated code contains instructions for creating the lookup table.

Replace the statement:

tbl = gettable(1024);

with:

tbl = coder.const(gettable(1024));

Generate code for getsine using an argument of type int32. Open the Code Generation Report.

The generated code contains the lookup table itself. coder.const forces the expression gettable(1024) to be evaluated during code generation. The generated code does not contain instructions for the evaluation. The generated code contains the result of the evaluation itself.

Write a function MultiplyConst that takes an input factor and multiplies every element of two vectors vec1 and vec2 with factor. The function generates vec1 and vec2 using another function EvalConsts.

function [y1,y2] = MultiplyConst(factor) %#codegen
  [vec1,vec2]=EvalConsts(pi.*(1./2.^(1:10)),2);
  y1=vec1.*factor;
  y2=vec2.*factor;

function [f1,f2]=EvalConsts(z,n)
  f1=z.^(2*n)/factorial(2*n);
  f2=z.^(2*n+1)/factorial(2*n+1);

Generate code for MultiplyConst using the codegen command. Open the Code Generation Report.

codegen -config:lib -launchreport MultiplyConst -args 0

The code generator produces code for creating the vectors.

Replace the statement

[vec1,vec2]=EvalConsts(pi.*(1./2.^(1:10)),2);

with

[vec1,vec2]=coder.const(@EvalConsts,pi.*(1./2.^(1:10)),2);

Generate code for MultiplyConst using the codegen command. Open the Code Generation Report.

codegen -config:lib -launchreport MultiplyConst -args 0

Write an XML file MyParams.xml containing the following statements:

<params>
    <param name="hello" value="17"/>
    <param name="world" value="42"/>
</params>

Save MyParams.xml in the current folder.

Write a MATLAB^® function xml2struct that reads an XML file. The function identifies the XML tag param inside another tag params.

After identifying param, the function assigns the value of its attribute name to the field name of a structure s. The function also assigns the value of attribute value to the value of the field.

function s = xml2struct(file)

s = struct();
doc = xmlread(file);
els = doc.getElementsByTagName('params');
for i = 0:els.getLength-1
    it = els.item(i);
    ps = it.getElementsByTagName('param');
    for j = 0:ps.getLength-1
        param = ps.item(j);
        paramName = char(param.getAttribute('name'));
        paramValue = char(param.getAttribute('value'));
        paramValue = evalin('base', paramValue);
        s.(paramName) = paramValue;        
    end
end

Save xml2struct in the current folder.

Write a MATLAB function MyFunc that reads the XML file MyParams.xml into a structure s using the function xml2struct. Declare xml2struct as extrinsic using coder.extrinsic and call it in a coder.const statement.

function y = MyFunc(u) %#codegen
  assert(isa(u, 'double'));
  coder.extrinsic('xml2struct');
  s = coder.const(xml2struct('MyParams.xml'));
  y = s.hello + s.world + u;

Generate code for MyFunc using the codegen command. Open the Code Generation Report.

codegen -config:dll -launchreport MyFunc -args 0

The code generator executes the call to xml2struct during code generation. It replaces the structure fields s.hello and s.world with the values 17 and 42 in generated code.