How to implement CPSat addDifferent with IntVar and LinearExpression in Java

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I'm back at Linear Expressions with Google Or Tools CP Sat in Java. Clunky doesn't describe it even close, Java is a mess here.

My goal is to add a constant to my IntVar and exclude this value for the next IntVar.

(Btw. it's already awkward how i add a constant to my IntVar, is there any other way?)

IntVar a = model.newIntVar(0, someValue, "a");
IntVar b = model.newIntVar(0, someValue, "b");
IntVar one = model.newIntVar(1, 1, "I have to do this");

LinearExpr expr = LinearExpr.scalProd(new IntVar[] {a, one}, new int[] {1, constant}) // a + constant
model.addDifferent(b, expr) // Error because addDifferent is only usable with (IntVar, IntVar)

How can I implement addDifferent with IntVar and LinearExpression?

cp-sat-solver or-tools optimization java
1 Answers

Indeed. The API is too restrictive.

option 1: You will need to create a new variable, bind it to the expression and use it in addDifferent

option 2:

 // write  b - a != constant 
 model.addDifferent(LinearExpr::scalProd(new IntVar[] {a, b}, new long[] {-1, 1}), constant);
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