1using System;
 2
 3namespace presentation.windows.server.domain.accounting
 4{
 5    public class Quantity : IEquatable<Quantity>
 6    {
 7        double amount;
 8        UnitOfMeasure units;
 9
10        public Quantity(double amount, UnitOfMeasure units)
11        {
12            this.units = units;
13            this.amount = amount;
14        }
15
16        public Quantity plus(Quantity other)
17        {
18            return new Quantity(amount + other.convert_to(units).amount, units);
19        }
20
21        public Quantity subtract(Quantity other)
22        {
23            return new Quantity(amount - other.convert_to(units).amount, units);
24        }
25
26        public Quantity convert_to(UnitOfMeasure unit_of_measure)
27        {
28            return new Quantity(unit_of_measure.convert(amount, units), unit_of_measure);
29        }
30
31        static public implicit operator double(Quantity quanity)
32        {
33            return quanity.amount;
34        }
35
36        public bool Equals(Quantity other)
37        {
38            if (ReferenceEquals(null, other)) return false;
39            if (ReferenceEquals(this, other)) return true;
40            return other.amount.Equals(amount) && Equals(other.units, units);
41        }
42
43        public override bool Equals(object obj)
44        {
45            if (ReferenceEquals(null, obj)) return false;
46            if (ReferenceEquals(this, obj)) return true;
47            if (obj.GetType() != typeof (Quantity)) return false;
48            return Equals((Quantity) obj);
49        }
50
51        public override int GetHashCode()
52        {
53            unchecked
54            {
55                return (amount.GetHashCode()*397) ^ (units != null ? units.GetHashCode() : 0);
56            }
57        }
58
59        public override string ToString()
60        {
61            return units.pretty_print(amount);
62        }
63    }
64}