All keyed collections use custom key semantics by providing an IEqualityComparer<T> or IComparer<T> instance. You have to provide on of these unless your key type implements IEquatable<T> or IComparable<T>, in which case the default is used.
You can create instances that use custom key semantics using the Helper classes.
ImmSet<string> setWithComparer = ImmSet.Empty<string>(MyEqComparer);
ImmMap<string> mapWithComparer = ImmMap.Empty<string>(MyEqComparer);You can also use extension methods defined directly on the key semantics objects.
var sortedMap = comparer.CreateSortedMap<int, string>();
var map = eqComparer.CreateMap<int, int>();Inheritance
New collection instances inherit the key semantics used by their source collection. It’s not possible to change the key semantics of a collection after it has been created.
Compatibility
Imms keyed collections support high-performance set-theoretic operations. These operations only work when all inputs are compatible. This means that their key semantics must be identical. Imms checks this using the following code, which defaults to reference equality:
set.EqualityComparer.Equals(otherSet.EqualityComparer);If you provide an incompatible collection, it will instead be treated as a n IEnumerable<T> and the high-performance implementation won’t be used.
All keyed and sorted collections support custom comparison logic via IComparer<T> or IEqualityComparer<T> instances, as well as default behavior for keys that implement IEquatable<T> or IComparable<T>.