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Immutable relations for .NET

NuGet link: https://www.nuget.org/packages/ImmutableRelations

This repository provides a C# implementation for immutable, n-ary relations. In all brevity:

• Relation is meant in the mathematical/computational/database sense: A set of tuples. In particular, the data structure is intended to serve as an efficient in-memory implementation of the binary-relational storage structure that R. A. Frost described more than 3.5 decades ago (despite that the library author would call the described relation ternary rather than binary).
• n-ary means that the data structure can principally manage relations of any arity. The most common use case is surely modeling binary relations. However, it also useful for unary relations - in which case the data structure degenerates simply to a (hash) set. Ternary relations are supported as well. Relations of higher arity can be supported by implementing a custom version of the ITupleAdapter<TupleType> interface. Disclaimer: Managing high-dimensional data is a challenging topic. Don't expect too much in terms of space/time efficiency when going beyond 3 dimensions.
• Immutable means that each modification of the data structure returns a new instance of it, keeping the original one unmodified. You may already know this principle from functional programming or System.Collections.Immutable (part of .NET Core and available on NuGet.org).