PredicateMap 1.0.1

PredicateMap

PredicateMap is a high-performance .NET library that allows you to map keys to values using predicates and direct key lookups. It compiles the mapping logic into an optimized expression tree, providing fast lookups even with complex conditions.

Features

• Fast Lookups: Compiles mapping logic into a single delegate using Expression Trees.
• Flexible Mapping: Supports both direct key-to-value mapping and predicate-based mapping.
• Priority Support: PriorityPredicateMapBuilder allows defining order-sensitive mappings.
• Fluent API: Easy-to-use builder pattern and extension methods.

Installation

Install the package via NuGet:

dotnet add package PredicateMap

Usage

Basic Usage with PredicateMapBuilder

Use PredicateMapBuilder when you have a mix of specific keys and general predicates.

using PredicateMap;
using System.Linq.Expressions;

var builder = new PredicateMapBuilder<int, string>()
    // Direct key mapping
    .Add(1, "One")
    .Add(2, "Two")
    // Predicate mapping
    .Add(x => x > 10, "Greater than ten")
    .Add(x => x < 0, "Negative");

IPredicateMap<int, string> map = builder.ToPredicateMap();

if (map.TryGet(1, out var value))
{
    Console.WriteLine(value); // Output: One
}

if (map.TryGet(15, out value))
{
    Console.WriteLine(value); // Output: Greater than ten
}

Priority Mapping with PriorityPredicateMapBuilder

Use PriorityPredicateMapBuilder when the order of evaluation matters. The first matching predicate or key will return the value.

using PredicateMap;

var builder = new PriorityPredicateMapBuilder<int, string>()
    // Order matters here
    .Add(x => x % 2 == 0, "Even")
    .Add(x => x % 3 == 0, "Divisible by 3")
    .Add(6, "Six"); // This will never be reached because 6 is Even

IPredicateMap<int, string> map = builder.ToPredicateMap();

map.TryGet(6, out var val1); // Output: Even
map.TryGet(9, out var val2); // Output: Divisible by 3

Creating from an Enumerable

You can also create a map from any IEnumerable<T> using the ToPredicateMap extension method.

var items = new[] { 1, 2, 3, 4, 5 };

IPredicateMap<int, string> map = items.ToPredicateMap(
    keySelector: x => x,
    valueSelector: x => x % 2 == 0 ? "Even" : "Odd"
);

Performance

PredicateMap is designed for performance. It compiles the lookup logic into a highly optimized delegate, minimizing overhead during runtime lookups. This makes it suitable for hot paths where performance is critical.