/src/LinFu.Finders/PredicateExtensions.cs

 1using System;
 2
 3namespace LinFu.Finders
 4{
 5    /// <summary>
 6    ///     A class that adds logical extensions to the <see cref="Func{T,TResult}" /> predicate
 7    ///     class.
 8    /// </summary>
 9    public static class PredicateExtensions
10    {
11        /// <summary>
12        ///     Logically ORs two <see cref="Func{T,TResult}" /> predicates together.
13        /// </summary>
14        /// <typeparam name="TItem">The type of item being compared.</typeparam>
15        /// <param name="left">The left hand predicate.</param>
16        /// <param name="right">The right hand predicate.</param>
17        /// <returns>
18        ///     A predicate that will return <c>true</c> if and only if one of the given predicates is <c>true</c>; otherwise,
19        ///     it will return <c>false</c>.
20        /// </returns>
21        public static Func<TItem, bool> Or<TItem>(this Func<TItem, bool> left, Func<TItem, bool> right)
22        {
23            return item => left(item) || right(item);
24        }
25
26        /// <summary>
27        ///     Logically ANDs two <see cref="Func{T,TResult}" /> predicates together.
28        /// </summary>
29        /// <typeparam name="TItem">The type of item being compared.</typeparam>
30        /// <param name="left">The left hand predicate.</param>
31        /// <param name="right">The right hand predicate.</param>
32        /// <returns>
33        ///     A predicate that will return <c>true</c> if and only if both of the given predicates are <c>true</c>;
34        ///     otherwise, it will return <c>false</c>.
35        /// </returns>
36        public static Func<TItem, bool> And<TItem>(this Func<TItem, bool> left, Func<TItem, bool> right)
37        {
38            return item => left(item) && right(item);
39        }
40
41        /// <summary>
42        ///     Logically negates a single predicate.
43        /// </summary>
44        /// <typeparam name="TItem">The type of item being compared.</typeparam>
45        /// <param name="predicate">The predicate to negate.</param>
46        /// <returns>Returns <c>true</c> if the given predicate is <c>false</c>.</returns>
47        public static Func<TItem, bool> Inverse<TItem>(this Func<TItem, bool> predicate)
48        {
49            return item => !predicate(item);
50        }
51    }
52}