Originally posted by: SystemAdmin

[gyvahn said:]

I'm writing a code in c++ to get and change the coefficients from a given problem.

I've come across IloExpr::LinearIterator and how to use getCoef() in the user manual; except the example doesn't work.

When I try the example

IloExpr e = 2*x + 3*y + cos(x);
IloExpr::LinearIterator it(e);      <

---

this line doesn&#039;t work so the code stops here.<br />
it.ok(); // returns IloTrue 
it.getCoef(); // returns 2 from the term (2*x)

Any suggestions?
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#DecisionOptimization

Originally posted by: SystemAdmin

[Sylvain said:]

The expression you define is nonlinear (cos) so you cannot you a linear iterator on it.
Try without cos(x).
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#DecisionOptimization

Originally posted by: SystemAdmin

[alain.chabrier said:]

Hi,

the IloExpr::LinearIterator should work with all expressions, althought it will only iterate on the linear part.

In your example, you should use IloCos instead of cos.

Then the way to get the iterator is using the getLinearIterator method.

Working code is :


int issue(IloEnv env) {
IloCplex cplex(env);

  IloNumVar x(env), y(env);
  IloExpr e = 2*x + 3*y + IloCos(x);
  IloExpr::LinearIterator it = e.getLinearIterator();   

  it.ok(); // returns IloTrue
  cout << it.getCoef() << endl; // returns 2 from the term (2*x)
  cout << it.getVar() << endl;<br />
cplex.end();
return 0;
}
#CPLEXOptimizers
#DecisionOptimization

Originally posted by: SystemAdmin

[gyvahn said:]

thank you! but how do I iterate over "it"? I would like to access all the coefficients one by one.
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#DecisionOptimization

Originally posted by: SystemAdmin

[oussedik said:]

Hi,

To iterate ove it you need to use,

while (it.ok()) {
cout << it.getCoef() << endl;<br />....

Sofiane
#CPLEXOptimizers
#DecisionOptimization

Originally posted by: SystemAdmin

[alain.chabrier said:]

You also need

it.next();

to go to the next one.

Alain

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#DecisionOptimization