ConstraintSolverTests.cs

// Copyright 2010-2022 Google LLC
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

using System;
using Xunit;
using Google.OrTools.ConstraintSolver;
using static Google.OrTools.ConstraintSolver.operations_research_constraint_solver;

namespace Google.OrTools.Tests
{
public class ConstraintSolverTest
{
    [Fact]
    public void IntVectorToInt64Vector()
    {
        int[] input = { 5, 11, 17 };
        long[] output = ToInt64Vector(input);
        Assert.Equal(3, output.Length);
        Assert.Equal(5, output[0]);
        Assert.Equal(11, output[1]);
        Assert.Equal(17, output[2]);
    }

    [Fact]
    public void IntVarConstructor()
    {
        Solver solver = new Solver("Solver");
        IntVar x = solver.MakeIntVar(3, 7, "x");
        Assert.Equal(3, x.Min());
        Assert.Equal(7, x.Max());
        Assert.Equal("x(3..7)", x.ToString());
    }

    [Fact]
    public void ConstraintConstructor()
    {
        Solver solver = new Solver("Solver");
        IntVar x = solver.MakeIntVar(3, 7, "x");
        Assert.Equal("x(3..7)", x.ToString());

        // Unary operator
        Constraint c0 = (x == 5);
        Assert.Equal("(x(3..7) == 5)", c0.ToString());
        IntExpr e1 = -c0;
        Assert.Equal("-(Watch<x == 5>(0 .. 1))", e1.ToString());
        IntExpr e2 = c0.Abs();
        Assert.Equal("Watch<x == 5>(0 .. 1)", e2.ToString());
        IntExpr e3 = c0.Square();
        Assert.Equal("IntSquare(Watch<x == 5>(0 .. 1))", e3.ToString());

        // Relational operator with a scalar
        Constraint c1 = x == 5;
        Assert.Equal("(x(3..7) == 5)", c1.ToString());
        Constraint c2 = x >= 5;
        Assert.Equal("(x(3..7) >= 5)", c2.ToString());
        Constraint c3 = x > 5;
        Assert.Equal("(x(3..7) >= 6)", c3.ToString());
        Constraint c4 = x <= 5;
        Assert.Equal("(x(3..7) <= 5)", c4.ToString());
        Constraint c5 = x < 5;
        Assert.Equal("(x(3..7) <= 4)", c5.ToString());
        Constraint c6 = x != 5;
        Assert.Equal("(x(3..7) != 5)", c6.ToString());
        Constraint c7 = x == 2;
        Assert.Equal("FalseConstraint()", c7.ToString());
    }

    [Fact]
    public void IntExprConstructor()
    {
        Solver solver = new Solver("Solver");
        IntVar x = solver.MakeIntVar(3, 13, "x");
        Assert.Equal(3, x.Min());
        Assert.Equal(13, x.Max());

        // Unary Operator
        IntExpr e1 = -(x == 7);
        Assert.Equal("-(Watch<x == 7>(0 .. 1))", e1.ToString());
        IntExpr e2 = (x == 7).Abs();
        Assert.Equal("Watch<x == 7>(0 .. 1)", e2.ToString());
        IntExpr e3 = (x == 7).Square();
        Assert.Equal("IntSquare(Watch<x == 7>(0 .. 1))", e3.ToString());
    }

    [Fact]
    public void GreaterIntExprConstructor()
    {
        Solver solver = new Solver("Solver");
        IntVar x = solver.MakeIntVar(3, 13, "x");
        Assert.Equal(3, x.Min());
        Assert.Equal(13, x.Max());

        // Unary Operator
        IntExpr e1 = -(x >= 7);
        Assert.Equal("-(Watch<x >= 7>(0 .. 1))", e1.ToString());
        IntExpr e2 = (x >= 7).Abs();
        Assert.Equal("Watch<x >= 7>(0 .. 1)", e2.ToString());
        IntExpr e3 = (x >= 7).Square();
        Assert.Equal("IntSquare(Watch<x >= 7>(0 .. 1))", e3.ToString());
    }

    [Fact]
    public void ConstraintAndScalar()
    {
        Solver solver = new Solver("Solver");
        IntVar x = solver.MakeIntVar(3, 13, "x");
        Assert.Equal(3, x.Min());
        Assert.Equal(13, x.Max());

        Constraint c1 = (x == 7);
        Assert.Equal("(x(3..13) == 7)", c1.ToString());

        // Arithmetic operator with a scalar
        IntExpr e2a = c1 + 1;
        Assert.Equal("(Watch<x == 7>(0 .. 1) + 1)", e2a.ToString());
        IntExpr e2b = 1 + c1;
        Assert.Equal("(Watch<x == 7>(0 .. 1) + 1)", e2b.ToString());

        IntExpr e2c = c1 - 1;
        Assert.Equal("(Watch<x == 7>(0 .. 1) + -1)", e2c.ToString());
        IntExpr e2d = 1 - c1;
        Assert.Equal("Not(Watch<x == 7>(0 .. 1))", e2d.ToString());

        IntExpr e2e = c1 * 2;
        Assert.Equal("(Watch<x == 7>(0 .. 1) * 2)", e2e.ToString());
        IntExpr e2f = 2 * c1;
        Assert.Equal("(Watch<x == 7>(0 .. 1) * 2)", e2f.ToString());

        IntExpr e2g = c1 / 4;
        Assert.Equal("(Watch<x == 7>(0 .. 1) div 4)", e2g.ToString());

        // Relational operator with a scalar
        Constraint c8a = c1 == 1;
        Assert.Equal("(Watch<x == 7>(0 .. 1) == 1)", c8a.ToString());
        Constraint c8b = 1 == c1;
        Assert.Equal("(Watch<x == 7>(0 .. 1) == 1)", c8b.ToString());

        Constraint c8c = c1 != 1;
        Assert.Equal("(Watch<x == 7>(0 .. 1) != 1)", c8c.ToString());
        Constraint c8d = 1 != c1;
        Assert.Equal("(Watch<x == 7>(0 .. 1) != 1)", c8d.ToString());

        Constraint c8e = c1 >= 1;
        Assert.Equal("(Watch<x == 7>(0 .. 1) >= 1)", c8e.ToString());
        Constraint c8f = 1 >= c1;
        Assert.Equal("TrueConstraint()", c8f.ToString());

        Constraint c8g = c1 > 1;
        Assert.Equal("FalseConstraint()", c8g.ToString());
        Constraint c8h = 1 > c1;
        Assert.Equal("(Watch<x == 7>(0 .. 1) <= 0)", c8h.ToString());

        Constraint c8i = c1 <= 1;
        Assert.Equal("TrueConstraint()", c8i.ToString());
        Constraint c8j = 1 <= c1;
        Assert.Equal("(Watch<x == 7>(0 .. 1) >= 1)", c8j.ToString());

        Constraint c8k = c1 < 1;
        Assert.Equal("(Watch<x == 7>(0 .. 1) <= 0)", c8k.ToString());
        Constraint c8l = 1 < c1;
        Assert.Equal("FalseConstraint()", c8l.ToString());
    }

    [Fact]
    public void ConstraintAndIntVar()
    {
        Solver solver = new Solver("Solver");
        IntVar x = solver.MakeIntVar(3, 13, "x");
        Assert.Equal(3, x.Min());
        Assert.Equal(13, x.Max());

        Constraint c1 = x == 7;
        Assert.Equal("(x(3..13) == 7)", c1.ToString());

        IntVar y = solver.MakeIntVar(5, 17, "y");
        Assert.Equal(5, y.Min());
        Assert.Equal(17, y.Max());

        // Arithmetic operator with IntVar
        IntExpr e3a = c1 + y;
        Assert.Equal("(Watch<x == 7>(0 .. 1) + y(5..17))", e3a.ToString());
        IntExpr e3b = y + c1;
        Assert.Equal("(Watch<x == 7>(0 .. 1) + y(5..17))", e3b.ToString());

        IntExpr e3c = c1 - y;
        Assert.Equal("(Watch<x == 7>(0 .. 1) - y(5..17))", e3c.ToString());
        IntExpr e3d = y - c1;
        Assert.Equal("(y(5..17) - Watch<x == 7>(0 .. 1))", e3d.ToString());

        IntExpr e3e = c1 * y;
        Assert.Equal("(Watch<x == 7>(0 .. 1) * y(5..17))", e3e.ToString());
        IntExpr e3f = y * c1;
        Assert.Equal("(Watch<x == 7>(0 .. 1) * y(5..17))", e3f.ToString());

        // Relational operator with an IntVar
        Constraint c9a = c1 == y;
        Assert.Equal("Watch<x == 7>(0 .. 1) == y(5..17)", c9a.ToString());
        Constraint c9b = y == c1;
        Assert.Equal("y(5..17) == Watch<x == 7>(0 .. 1)", c9b.ToString());

        Constraint c9c = c1 != y;
        Assert.Equal("Watch<x == 7>(0 .. 1) != y(5..17)", c9c.ToString());
        Constraint c9d = y != c1;
        Assert.Equal("y(5..17) != Watch<x == 7>(0 .. 1)", c9d.ToString());

        Constraint c9e = c1 >= y;
        Assert.Equal("y(5..17) <= Watch<x == 7>(0 .. 1)", c9e.ToString());
        Constraint c9f = y >= c1;
        Assert.Equal("Watch<x == 7>(0 .. 1) <= y(5..17)", c9f.ToString());

        Constraint c9g = c1 > y;
        Assert.Equal("y(5..17) < Watch<x == 7>(0 .. 1)", c9g.ToString());
        Constraint c9h = y > c1;
        Assert.Equal("Watch<x == 7>(0 .. 1) < y(5..17)", c9h.ToString());

        Constraint c9i = c1 <= y;
        Assert.Equal("Watch<x == 7>(0 .. 1) <= y(5..17)", c9i.ToString());
        Constraint c9j = y <= c1;
        Assert.Equal("y(5..17) <= Watch<x == 7>(0 .. 1)", c9j.ToString());

        Constraint c9k = c1 < y;
        Assert.Equal("Watch<x == 7>(0 .. 1) < y(5..17)", c9k.ToString());
        Constraint c9l = y < c1;
        Assert.Equal("y(5..17) < Watch<x == 7>(0 .. 1)", c9l.ToString());
    }

    [Fact]
    public void ConstraintAndIntExpr()
    {
        Solver solver = new Solver("Solver");
        IntVar x = solver.MakeIntVar(3, 13, "x");
        Assert.Equal(3, x.Min());
        Assert.Equal(13, x.Max());
        Constraint c1 = x == 7;
        Assert.Equal("(x(3..13) == 7)", c1.ToString());

        IntVar y = solver.MakeIntVar(5, 17, "y");
        Assert.Equal(5, y.Min());
        Assert.Equal(17, y.Max());

        // Arithmetic operator with an IntExpr
        IntExpr e11a = c1 + (y == 11);
        Assert.Equal("(Watch<x == 7>(0 .. 1) + Watch<y == 11>(0 .. 1))", e11a.ToString());
        IntExpr e11b = (y == 11) + c1;
        Assert.Equal("(Watch<x == 7>(0 .. 1) + Watch<y == 11>(0 .. 1))", e11b.ToString());
        IntExpr e11c = c1 - (y == 11);
        Assert.Equal("(Watch<x == 7>(0 .. 1) - Watch<y == 11>(0 .. 1))", e11c.ToString());
        IntExpr e11d = (y == 11) - c1;
        Assert.Equal("(Watch<y == 11>(0 .. 1) - Watch<x == 7>(0 .. 1))", e11d.ToString());
        IntExpr e11e = c1 * (y == 11);
        Assert.Equal("(Watch<x == 7>(0 .. 1) * Watch<y == 11>(0 .. 1))", e11e.ToString());
        IntExpr e11f = (y == 11) * c1;
        Assert.Equal("(Watch<x == 7>(0 .. 1) * Watch<y == 11>(0 .. 1))", e11f.ToString());

        // Relational operator with an IntExpr
        Constraint c12a = c1 == (y == 11);
        Assert.Equal("Watch<x == 7>(0 .. 1) == Watch<y == 11>(0 .. 1)", c12a.ToString());
        Constraint c12b = (y == 11) == c1;
        Assert.Equal("Watch<y == 11>(0 .. 1) == Watch<x == 7>(0 .. 1)", c12b.ToString());
        Constraint c12c = c1 != (y == 11);
        Assert.Equal("Watch<x == 7>(0 .. 1) != Watch<y == 11>(0 .. 1)", c12c.ToString());
        Constraint c12d = (y == 11) != c1;
        Assert.Equal("Watch<y == 11>(0 .. 1) != Watch<x == 7>(0 .. 1)", c12d.ToString());
        Constraint c12e = c1 >= (y == 11);
        Assert.Equal("Watch<y == 11>(0 .. 1) <= Watch<x == 7>(0 .. 1)", c12e.ToString());
        Constraint c12f = (y == 11) >= c1;
        Assert.Equal("Watch<x == 7>(0 .. 1) <= Watch<y == 11>(0 .. 1)", c12f.ToString());
        Constraint c12g = c1 > (y == 11);
        Assert.Equal("Watch<y == 11>(0 .. 1) < Watch<x == 7>(0 .. 1)", c12g.ToString());
        Constraint c12h = (y == 11) > c1;
        Assert.Equal("Watch<x == 7>(0 .. 1) < Watch<y == 11>(0 .. 1)", c12h.ToString());
        Constraint c12i = c1 <= (y == 11);
        Assert.Equal("Watch<x == 7>(0 .. 1) <= Watch<y == 11>(0 .. 1)", c12i.ToString());
        Constraint c12j = (y == 11) <= c1;
        Assert.Equal("Watch<y == 11>(0 .. 1) <= Watch<x == 7>(0 .. 1)", c12j.ToString());
        Constraint c12k = c1 < (y == 11);
        Assert.Equal("Watch<x == 7>(0 .. 1) < Watch<y == 11>(0 .. 1)", c12k.ToString());
        Constraint c12l = (y == 11) < c1;
        Assert.Equal("Watch<y == 11>(0 .. 1) < Watch<x == 7>(0 .. 1)", c12l.ToString());
    }

    [Fact]
    public void ConstraintAndConstraint()
    {
        Solver solver = new Solver("Solver");
        IntVar x = solver.MakeIntVar(3, 13, "x");
        Assert.Equal(3, x.Min());
        Assert.Equal(13, x.Max());
        Constraint c1 = x == 7;
        Assert.Equal("(x(3..13) == 7)", c1.ToString());

        IntVar y = solver.MakeIntVar(5, 17, "y");
        Assert.Equal(5, y.Min());
        Assert.Equal(17, y.Max());
        Constraint c2 = y == 11;
        Assert.Equal("(y(5..17) == 11)", c2.ToString());

        // Relational operator with a Constraint
        Constraint c10a = c1 == c2;
        Assert.Equal("Watch<x == 7>(0 .. 1) == Watch<y == 11>(0 .. 1)", c10a.ToString());

        Constraint c10b = c1 != c2;
        Assert.Equal("Watch<x == 7>(0 .. 1) != Watch<y == 11>(0 .. 1)", c10b.ToString());

        Constraint c10c = c1 <= c2;
        Assert.Equal("Watch<x == 7>(0 .. 1) <= Watch<y == 11>(0 .. 1)", c10c.ToString());
        Constraint c10d = c1 >= c2;
        Assert.Equal("Watch<y == 11>(0 .. 1) <= Watch<x == 7>(0 .. 1)", c10d.ToString());

        Constraint c10e = c1 > c2;
        Assert.Equal("Watch<y == 11>(0 .. 1) < Watch<x == 7>(0 .. 1)", c10e.ToString());
        Constraint c10f = c1 < c2;
        Assert.Equal("Watch<x == 7>(0 .. 1) < Watch<y == 11>(0 .. 1)", c10f.ToString());
    }

    [Fact]
    public void IntExprAndScalar()
    {
        Solver solver = new Solver("Solver");
        IntVar x = solver.MakeIntVar(3, 13, "x");
        Assert.Equal(3, x.Min());
        Assert.Equal(13, x.Max());

        // Arithmetic operator with a scalar
        IntExpr e2a = (x == 7) + 1;
        Assert.Equal("(Watch<x == 7>(0 .. 1) + 1)", e2a.ToString());
        IntExpr e2b = 1 + (x == 7);
        Assert.Equal("(Watch<x == 7>(0 .. 1) + 1)", e2b.ToString());

        IntExpr e2c = (x == 7) - 1;
        Assert.Equal("(Watch<x == 7>(0 .. 1) + -1)", e2c.ToString());
        IntExpr e2d = 1 - (x == 7);
        Assert.Equal("Not(Watch<x == 7>(0 .. 1))", e2d.ToString());

        IntExpr e2e = (x == 7) * 2;
        Assert.Equal("(Watch<x == 7>(0 .. 1) * 2)", e2e.ToString());
        IntExpr e2f = 2 * (x == 7);
        Assert.Equal("(Watch<x == 7>(0 .. 1) * 2)", e2f.ToString());

        IntExpr e2g = (x == 7) / 4;
        Assert.Equal("(Watch<x == 7>(0 .. 1) div 4)", e2g.ToString());

        // Relational operator with a scalar
        Constraint c8a = (x == 7) == 1;
        Assert.Equal("(Watch<x == 7>(0 .. 1) == 1)", c8a.ToString());
        Constraint c8b = 1 == (x == 7);
        Assert.Equal("(Watch<x == 7>(0 .. 1) == 1)", c8b.ToString());

        Constraint c8c = (x == 7) != 1;
        Assert.Equal("(Watch<x == 7>(0 .. 1) != 1)", c8c.ToString());
        Constraint c8d = 1 != (x == 7);
        Assert.Equal("(Watch<x == 7>(0 .. 1) != 1)", c8d.ToString());

        Constraint c8e = (x == 7) >= 1;
        Assert.Equal("(Watch<x == 7>(0 .. 1) >= 1)", c8e.ToString());
        Constraint c8f = 1 >= (x == 7);
        Assert.Equal("TrueConstraint()", c8f.ToString());

        Constraint c8g = (x == 7) > 1;
        Assert.Equal("FalseConstraint()", c8g.ToString());
        Constraint c8h = 1 > (x == 7);
        Assert.Equal("(Watch<x == 7>(0 .. 1) <= 0)", c8h.ToString());

        Constraint c8i = (x == 7) <= 1;
        Assert.Equal("TrueConstraint()", c8i.ToString());
        Constraint c8j = 1 <= (x == 7);
        Assert.Equal("(Watch<x == 7>(0 .. 1) >= 1)", c8j.ToString());

        Constraint c8k = (x == 7) < 1;
        Assert.Equal("(Watch<x == 7>(0 .. 1) <= 0)", c8k.ToString());
        Constraint c8l = 1 < (x == 7);
        Assert.Equal("FalseConstraint()", c8l.ToString());
    }

    [Fact]
    public void IntExprAndIntVar()
    {
        Solver solver = new Solver("Solver");
        IntVar x = solver.MakeIntVar(3, 13, "x");
        Assert.Equal(3, x.Min());
        Assert.Equal(13, x.Max());

        IntVar y = solver.MakeIntVar(5, 17, "y");
        Assert.Equal(5, y.Min());
        Assert.Equal(17, y.Max());

        // Arithmetic operator with IntVar
        IntExpr e3a = (x == 7) + y;
        Assert.Equal("(Watch<x == 7>(0 .. 1) + y(5..17))", e3a.ToString());
        IntExpr e3b = y + (x == 7);
        Assert.Equal("(Watch<x == 7>(0 .. 1) + y(5..17))", e3b.ToString());

        IntExpr e3c = (x == 7) - y;
        Assert.Equal("(Watch<x == 7>(0 .. 1) - y(5..17))", e3c.ToString());
        IntExpr e3d = y - (x == 7);
        Assert.Equal("(y(5..17) - Watch<x == 7>(0 .. 1))", e3d.ToString());

        IntExpr e3e = (x == 7) * y;
        Assert.Equal("(Watch<x == 7>(0 .. 1) * y(5..17))", e3e.ToString());
        IntExpr e3f = y * (x == 7);
        Assert.Equal("(Watch<x == 7>(0 .. 1) * y(5..17))", e3f.ToString());

        // Relational operator with an IntVar
        Constraint c9a = (x == 7) == y;
        Assert.Equal("Watch<x == 7>(0 .. 1) == y(5..17)", c9a.ToString());
        Constraint c9b = y == (x == 7);
        Assert.Equal("y(5..17) == Watch<x == 7>(0 .. 1)", c9b.ToString());

        Constraint c9c = (x == 7) != y;
        Assert.Equal("Watch<x == 7>(0 .. 1) != y(5..17)", c9c.ToString());
        Constraint c9d = y != (x == 7);
        Assert.Equal("y(5..17) != Watch<x == 7>(0 .. 1)", c9d.ToString());

        Constraint c9e = (x == 7) >= y;
        Assert.Equal("y(5..17) <= Watch<x == 7>(0 .. 1)", c9e.ToString());
        Constraint c9f = y >= (x == 7);
        Assert.Equal("Watch<x == 7>(0 .. 1) <= y(5..17)", c9f.ToString());

        Constraint c9g = (x == 7) > y;
        Assert.Equal("y(5..17) < Watch<x == 7>(0 .. 1)", c9g.ToString());
        Constraint c9h = y > (x == 7);
        Assert.Equal("Watch<x == 7>(0 .. 1) < y(5..17)", c9h.ToString());

        Constraint c9i = (x == 7) <= y;
        Assert.Equal("Watch<x == 7>(0 .. 1) <= y(5..17)", c9i.ToString());
        Constraint c9j = y <= (x == 7);
        Assert.Equal("y(5..17) <= Watch<x == 7>(0 .. 1)", c9j.ToString());

        Constraint c9k = (x == 7) < y;
        Assert.Equal("Watch<x == 7>(0 .. 1) < y(5..17)", c9k.ToString());
        Constraint c9l = y < (x == 7);
        Assert.Equal("y(5..17) < Watch<x == 7>(0 .. 1)", c9l.ToString());
    }

    [Fact]
    public void IntExprAndIntExpr()
    {
        Solver solver = new Solver("Solver");
        IntVar x = solver.MakeIntVar(3, 13, "x");
        Assert.Equal(3, x.Min());
        Assert.Equal(13, x.Max());

        IntVar y = solver.MakeIntVar(5, 17, "y");
        Assert.Equal(5, y.Min());
        Assert.Equal(17, y.Max());

        // Relational operator between IntExpr
        Constraint c10a = (x == 7) == (y == 11);
        Assert.Equal("Watch<x == 7>(0 .. 1) == Watch<y == 11>(0 .. 1)", c10a.ToString());

        Constraint c10b = (x == 7) != (y == 11);
        Assert.Equal("Watch<x == 7>(0 .. 1) != Watch<y == 11>(0 .. 1)", c10b.ToString());

        Constraint c10c = (x == 7) <= (y == 11);
        Assert.Equal("Watch<x == 7>(0 .. 1) <= Watch<y == 11>(0 .. 1)", c10c.ToString());
        Constraint c10d = (x == 7) >= (y == 11);
        Assert.Equal("Watch<y == 11>(0 .. 1) <= Watch<x == 7>(0 .. 1)", c10d.ToString());

        Constraint c10e = (x == 7) > (y == 11);
        Assert.Equal("Watch<y == 11>(0 .. 1) < Watch<x == 7>(0 .. 1)", c10e.ToString());
        Constraint c10f = (x == 7) < (y == 11);
        Assert.Equal("Watch<x == 7>(0 .. 1) < Watch<y == 11>(0 .. 1)", c10f.ToString());
    }

    [Fact]
    public void GreaterIntExprAndScalar()
    {
        Solver solver = new Solver("Solver");
        IntVar x = solver.MakeIntVar(3, 13, "x");
        Assert.Equal(3, x.Min());
        Assert.Equal(13, x.Max());

        // Arithmetic operator with a scalar
        IntExpr e2a = (x >= 7) + 1;
        Assert.Equal("(Watch<x >= 7>(0 .. 1) + 1)", e2a.ToString());
        IntExpr e2b = 1 + (x >= 7);
        Assert.Equal("(Watch<x >= 7>(0 .. 1) + 1)", e2b.ToString());

        IntExpr e2c = (x >= 7) - 1;
        Assert.Equal("(Watch<x >= 7>(0 .. 1) + -1)", e2c.ToString());
        IntExpr e2d = 1 - (x >= 7);
        Assert.Equal("Not(Watch<x >= 7>(0 .. 1))", e2d.ToString());

        IntExpr e2e = (x >= 7) * 2;
        Assert.Equal("(Watch<x >= 7>(0 .. 1) * 2)", e2e.ToString());
        IntExpr e2f = 2 * (x >= 7);
        Assert.Equal("(Watch<x >= 7>(0 .. 1) * 2)", e2f.ToString());

        // Relational operator with a scalar
        Constraint c8a = (x >= 7) == 1;
        Assert.Equal("(Watch<x >= 7>(0 .. 1) == 1)", c8a.ToString());
        Constraint c8b = 1 == (x >= 7);
        Assert.Equal("(Watch<x >= 7>(0 .. 1) == 1)", c8b.ToString());

        Constraint c8c = (x >= 7) != 1;
        Assert.Equal("(Watch<x >= 7>(0 .. 1) != 1)", c8c.ToString());
        Constraint c8d = 1 != (x >= 7);
        Assert.Equal("(Watch<x >= 7>(0 .. 1) != 1)", c8d.ToString());

        Constraint c8e = (x >= 7) >= 1;
        Assert.Equal("(Watch<x >= 7>(0 .. 1) >= 1)", c8e.ToString());
        Constraint c8f = 1 >= (x >= 7);
        Assert.Equal("TrueConstraint()", c8f.ToString());

        Constraint c8g = (x >= 7) > 1;
        Assert.Equal("FalseConstraint()", c8g.ToString());
        Constraint c8h = 1 > (x >= 7);
        Assert.Equal("(Watch<x >= 7>(0 .. 1) <= 0)", c8h.ToString());

        Constraint c8i = (x >= 7) <= 1;
        Assert.Equal("TrueConstraint()", c8i.ToString());
        Constraint c8j = 1 <= (x >= 7);
        Assert.Equal("(Watch<x >= 7>(0 .. 1) >= 1)", c8j.ToString());

        Constraint c8k = (x >= 7) < 1;
        Assert.Equal("(Watch<x >= 7>(0 .. 1) <= 0)", c8k.ToString());
        Constraint c8l = 1 < (x >= 7);
        Assert.Equal("FalseConstraint()", c8l.ToString());
    }

    [Fact]
    public void GreaterIntExprAndIntVar()
    {
        Solver solver = new Solver("Solver");
        IntVar x = solver.MakeIntVar(3, 13, "x");
        Assert.Equal(3, x.Min());
        Assert.Equal(13, x.Max());

        IntVar y = solver.MakeIntVar(5, 17, "y");
        Assert.Equal(5, y.Min());
        Assert.Equal(17, y.Max());

        // Arithmetic operator with IntVar
        IntExpr e3a = (x >= 7) + y;
        Assert.Equal("(Watch<x >= 7>(0 .. 1) + y(5..17))", e3a.ToString());
        IntExpr e3b = y + (x >= 7);
        Assert.Equal("(Watch<x >= 7>(0 .. 1) + y(5..17))", e3b.ToString());

        IntExpr e3c = (x >= 7) - y;
        Assert.Equal("(Watch<x >= 7>(0 .. 1) - y(5..17))", e3c.ToString());
        IntExpr e3d = y - (x >= 7);
        Assert.Equal("(y(5..17) - Watch<x >= 7>(0 .. 1))", e3d.ToString());

        IntExpr e3e = (x >= 7) * y;
        Assert.Equal("(Watch<x >= 7>(0 .. 1) * y(5..17))", e3e.ToString());
        IntExpr e3f = y * (x >= 7);
        Assert.Equal("(Watch<x >= 7>(0 .. 1) * y(5..17))", e3f.ToString());

        // Relational operator with an IntVar
        Constraint c9a = (x >= 7) == y;
        Assert.Equal("Watch<x >= 7>(0 .. 1) == y(5..17)", c9a.ToString());
        Constraint c9b = y == (x >= 7);
        Assert.Equal("y(5..17) == Watch<x >= 7>(0 .. 1)", c9b.ToString());

        Constraint c9c = (x >= 7) != y;
        Assert.Equal("Watch<x >= 7>(0 .. 1) != y(5..17)", c9c.ToString());
        Constraint c9d = y != (x >= 7);
        Assert.Equal("y(5..17) != Watch<x >= 7>(0 .. 1)", c9d.ToString());

        Constraint c9e = (x >= 7) >= y;
        Assert.Equal("y(5..17) <= Watch<x >= 7>(0 .. 1)", c9e.ToString());
        Constraint c9f = y >= (x >= 7);
        Assert.Equal("Watch<x >= 7>(0 .. 1) <= y(5..17)", c9f.ToString());

        Constraint c9g = (x >= 7) > y;
        Assert.Equal("y(5..17) < Watch<x >= 7>(0 .. 1)", c9g.ToString());
        Constraint c9h = y > (x >= 7);
        Assert.Equal("Watch<x >= 7>(0 .. 1) < y(5..17)", c9h.ToString());

        Constraint c9i = (x >= 7) <= y;
        Assert.Equal("Watch<x >= 7>(0 .. 1) <= y(5..17)", c9i.ToString());
        Constraint c9j = y <= (x >= 7);
        Assert.Equal("y(5..17) <= Watch<x >= 7>(0 .. 1)", c9j.ToString());

        Constraint c9k = (x >= 7) < y;
        Assert.Equal("Watch<x >= 7>(0 .. 1) < y(5..17)", c9k.ToString());
        Constraint c9l = y < (x >= 7);
        Assert.Equal("y(5..17) < Watch<x >= 7>(0 .. 1)", c9l.ToString());
    }

    [Fact]
    public void GreaterIntExprAndGreaterIntExpr()
    {
        Solver solver = new Solver("Solver");
        IntVar x = solver.MakeIntVar(3, 13, "x");
        Assert.Equal(3, x.Min());
        Assert.Equal(13, x.Max());

        IntVar y = solver.MakeIntVar(5, 17, "y");
        Assert.Equal(5, y.Min());
        Assert.Equal(17, y.Max());

        // Relational operator between IntExpr
        Constraint c10a = (x >= 7) == (y >= 11);
        Assert.Equal("Watch<x >= 7>(0 .. 1) == Watch<y >= 11>(0 .. 1)", c10a.ToString());

        Constraint c10b = (x >= 7) != (y >= 11);
        Assert.Equal("Watch<x >= 7>(0 .. 1) != Watch<y >= 11>(0 .. 1)", c10b.ToString());

        Constraint c10c = (x >= 7) <= (y >= 11);
        Assert.Equal("Watch<x >= 7>(0 .. 1) <= Watch<y >= 11>(0 .. 1)", c10c.ToString());
        Constraint c10d = (x >= 7) >= (y >= 11);
        Assert.Equal("Watch<y >= 11>(0 .. 1) <= Watch<x >= 7>(0 .. 1)", c10d.ToString());

        Constraint c10e = (x >= 7) > (y >= 11);
        Assert.Equal("Watch<y >= 11>(0 .. 1) < Watch<x >= 7>(0 .. 1)", c10e.ToString());
        Constraint c10f = (x >= 7) < (y >= 11);
        Assert.Equal("Watch<x >= 7>(0 .. 1) < Watch<y >= 11>(0 .. 1)", c10f.ToString());
    }

    [Fact]
    public void Downcast()
    {
        Solver solver = new Solver("Solver");
        IntVar x = solver.MakeIntVar(2, 17, "x");
        IntExpr e = x + 5;
        IntVar y = e.Var();
        Assert.Equal("(x(2..17) + 5)", y.ToString());
    }

    [Fact]
    public void Sequence()
    {
        Solver solver = new Solver("Solver");
        IntervalVar[] intervals = solver.MakeFixedDurationIntervalVarArray(10, 0, 10, 5, false, "task");
        DisjunctiveConstraint disjunctive = intervals.Disjunctive("Sequence");
        SequenceVar var = disjunctive.SequenceVar();
        Assignment ass = solver.MakeAssignment();
        ass.Add(var);
        ass.SetForwardSequence(var, new int[] { 1, 3, 5 });
        int[] seq = ass.ForwardSequence(var);
        Assert.Equal(3, seq.Length);
        Assert.Equal(1, seq[0]);
        Assert.Equal(3, seq[1]);
        Assert.Equal(5, seq[2]);
    }

    // A simple demon that simply sets the maximum of a fixed IntVar to 10 when
    // it's being called.
    class SetMaxDemon : NetDemon
    {
        public SetMaxDemon(IntVar x)
        {
            x_ = x;
        }
        public override void Run(Solver s)
        {
            x_.SetMax(10);
        }
        private IntVar x_;
    }

    [Fact]
    public void Demon()
    {
        Solver solver = new Solver("DemonTest");
        IntVar x = solver.MakeIntVar(new int[] { 2, 4, -1, 6, 11, 10 }, "x");
        NetDemon demon = new SetMaxDemon(x);
        Assert.Equal(11, x.Max());
        demon.Run(solver);
        Assert.Equal(10, x.Max());
    }

    // This constraint has a single target variable x. It enforces x >= 5 upon
    // InitialPropagate() and invokes the SetMaxDemon when x changes its range.
    class SetMinAndMaxConstraint : NetConstraint
    {
        public SetMinAndMaxConstraint(Solver solver, IntVar x) : base(solver)
        {
            x_ = x;
        }
        public override void Post()
        {
            // Always store the demon in the constraint to avoid it being reclaimed
            // by the GC.
            demon_ = new SetMaxDemon(x_);
            x_.WhenBound(demon_);
        }
        public override void InitialPropagate()
        {
            x_.SetMin(5);
        }
        private IntVar x_;
        private Demon demon_;
    }

    [Fact]
    public void MinAndMaxConstraint()
    {
        Solver solver = new Solver("TestConstraint");
        IntVar x = solver.MakeIntVar(new int[] { 2, 4, -1, 6, 11, 10 }, "x");
        Constraint ct = new SetMinAndMaxConstraint(solver, x);
        solver.Add(ct);
        DecisionBuilder db = solver.MakePhase(x, Solver.CHOOSE_FIRST_UNBOUND, Solver.ASSIGN_MIN_VALUE);
        solver.NewSearch(db);
        Assert.Equal(-1, x.Min());
        Assert.Equal(11, x.Max());

        Assert.True(solver.NextSolution());
        Assert.Equal(6, x.Min());
        Assert.Equal(6, x.Max());

        Assert.True(solver.NextSolution());
        Assert.Equal(10, x.Min());
        Assert.Equal(10, x.Max());

        Assert.False(solver.NextSolution());
        solver.EndSearch();
    }

    // // This constraint has a single target variable x. It enforces x >= 5,
    // but only at the leaf of the search tree: it doesn't change x's bounds,
    // and simply fails if x is bound and is < 5.
    class DumbGreaterOrEqualToFive : NetConstraint
    {
        public DumbGreaterOrEqualToFive(Solver solver, IntVar x) : base(solver)
        {
            x_ = x;
        }
        public override void Post()
        {
            demon_ = solver().MakeConstraintInitialPropagateCallback(this);
            x_.WhenRange(demon_);
        }
        public override void InitialPropagate()
        {
            if (x_.Bound())
            {
                if (x_.Value() < 5)
                {
                    solver().Fail();
                }
            }
        }
        private IntVar x_;
        private Demon demon_;
    }

    [Fact]
    public void FailingConstraint()
    {
        Solver solver = new Solver("TestConstraint");
        IntVar x = solver.MakeIntVar(new int[] { 2, 4, -1, 6, 11, 10 }, "x");
        Constraint ct = new DumbGreaterOrEqualToFive(solver, x);
        solver.Add(ct);
        DecisionBuilder db = solver.MakePhase(x, Solver.CHOOSE_FIRST_UNBOUND, Solver.ASSIGN_MIN_VALUE);
        solver.NewSearch(db);
        Assert.True(solver.NextSolution());
        Assert.Equal(6, x.Min());
        solver.EndSearch();
    }

    [Fact]
    public void DomainIterator()
    {
        Solver solver = new Solver("TestConstraint");
        IntVar x = solver.MakeIntVar(new int[] { 2, 4, -1, 6, 11, 10 }, "x");
        ulong count = 0;
        foreach (long value in x.GetDomain())
        {
            count++;
        }
        Assert.Equal(count, x.Size());
    }

    class CountHoles : NetDemon
    {
        public CountHoles(IntVar x)
        {
            x_ = x;
            count_ = 0;
        }
        public override void Run(Solver s)
        {
            foreach (long removed in x_.GetHoles())
            {
                count_++;
            }
        }
        public int count()
        {
            return count_;
        }
        private IntVar x_;
        private int count_;
    }

    class RemoveThreeValues : NetConstraint
    {
        public RemoveThreeValues(Solver solver, IntVar x) : base(solver)
        {
            x_ = x;
        }
        public override void Post()
        {
            demon_ = new CountHoles(x_);
            x_.WhenDomain(demon_);
        }
        public override void InitialPropagate()
        {
            x_.RemoveValues(new long[] { 3, 5, 7 });
        }
        public int count()
        {
            return demon_.count();
        }
        private IntVar x_;
        private CountHoles demon_;
    }

    [Fact]
    public void HoleIteratorTest()
    {
        Solver solver = new Solver("TestConstraint");
        IntVar x = solver.MakeIntVar(0, 10, "x");
        RemoveThreeValues ct = new RemoveThreeValues(solver, x);
        solver.Add(ct);
        DecisionBuilder db = solver.MakePhase(x, Solver.CHOOSE_FIRST_UNBOUND, Solver.ASSIGN_MIN_VALUE);
        solver.Solve(db);
        Assert.Equal(3, ct.count());
    }

    // TODO(user): Improve search log tests; currently only tests coverage.
    void RunSearchLog(in SearchMonitor searchlog)
    {
        searchlog.EnterSearch();
        searchlog.ExitSearch();
        searchlog.AcceptSolution();
        searchlog.AtSolution();
        searchlog.BeginFail();
        searchlog.NoMoreSolutions();
        searchlog.BeginInitialPropagation();
        searchlog.EndInitialPropagation();
    }

    [Fact]
    public void SearchLog()
    {
        Solver solver = new Solver("TestSearchLog");
        IntVar var = solver.MakeIntVar(1, 1, "Variable");
        OptimizeVar objective = solver.MakeMinimize(var, 1);
        SearchMonitor searchlog = solver.MakeSearchLog(0);
        RunSearchLog(in searchlog);
        GC.KeepAlive(solver);
    }

    [Theory]
    [InlineData(false)]
    [InlineData(true)]
    public void SearchLogWithCallback(bool callGC)
    {
        Solver solver = new Solver("TestSearchLog");
        IntVar var = solver.MakeIntVar(1, 1, "Variable");
        OptimizeVar objective = solver.MakeMinimize(var, 1);
        int count = 0;
        SearchMonitor searchlog = solver.MakeSearchLog(0, // branch period
                                                       () =>
                                                       {
                                                           count++;
                                                           return "display callback...";
                                                       });
        if (callGC)
        {
            GC.Collect();
            GC.WaitForPendingFinalizers();
        }
        RunSearchLog(in searchlog);
        GC.KeepAlive(solver);
        Assert.Equal(1, count);
    }

    [Theory]
    [InlineData(false)]
    [InlineData(true)]
    public void SearchLogWithObjectiveAndCallback(bool callGC)
    {
        Solver solver = new Solver("TestSearchLog");
        IntVar var = solver.MakeIntVar(1, 1, "Variable");
        OptimizeVar objective = solver.MakeMinimize(var, 1);
        int count = 0;
        SearchMonitor searchlog = solver.MakeSearchLog(0,         // branch period
                                                       objective, // objective var to monitor
                                                       () =>
                                                       {
                                                           count++;
                                                           return "OptimizeVar display callback";
                                                       });
        if (callGC)
        {
            GC.Collect();
            GC.WaitForPendingFinalizers();
        }
        RunSearchLog(in searchlog);
        GC.KeepAlive(solver);
        Assert.Equal(1, count);
    }

    [Theory]
    [InlineData(false)]
    [InlineData(true)]
    public void SearchLogWithIntVarAndCallback(bool callGC)
    {
        Solver solver = new Solver("TestSearchLog");
        IntVar var = solver.MakeIntVar(1, 1, "Variable");
        OptimizeVar objective = solver.MakeMinimize(var, 1);
        int count = 0;
        SearchMonitor searchlog = solver.MakeSearchLog(0,   // branch period
                                                       var, // int var to monitor
                                                       () =>
                                                       {
                                                           count++;
                                                           return "IntVar display callback";
                                                       });
        if (callGC)
        {
            GC.Collect();
            GC.WaitForPendingFinalizers();
        }
        RunSearchLog(in searchlog);
        GC.KeepAlive(solver);
        Assert.Equal(1, count);
    }
}
} // namespace Google.OrTools.Tests