/// <summary> Gets the canonical signature (the constant set containing all elements allowed by the parameters) designated by the specified parameters, or created it if necessary. </summary>
/// <param name="parameter"> The set of elements acceptable as argument. </param>
/// <param name="result"> The set of returnable elements. </param>
/// <param name="debuggingDescription"> A debugging-purpose description of this set. Specifiy null to use the default form. </param>
public static Signature From(ISet parameter, ISet result, string debuggingDescription = null)
{
Contract.Requires(parameter != null);
Contract.Requires(result != null);
Contract.Requires(new[] { parameter, result }.Select(element => element.Workspace).AreEqual(ReferenceEqualityComparer));
Contract.Requires(genericSignatureDefinition.Parameter.Supersets(parameter));
Contract.Requires(genericSignatureDefinition.Result.Supersets(result));
Func<ISet, Signature> create;
if (parameter as Set == null || result as Set == null)
{
//TODO: return signature definition if both result and parameter are unconstrained variable sets
create = _ =>
{
var potentialParameters = new[] { parameter as VariableSet, result as VariableSet };
ReadOnlyCollection<VariableSet> newParameters = potentialParameters.Where(NotNull).ToReadOnlyList();
ReadOnlyCollection<Variance> newVariances = potentialParameters.ZipWhere(signatureVariances, (p, variance) => p != null, (p, variance) => variance).ToReadOnlyList(2);
return new Signature(new[] { parameter, result }.ToReadOnlyList(), newParameters, newVariances, debuggingDescription);
};
}
else
{
create = _ => new Signature(new[] { parameter, result }.ToReadOnlyList(), debuggingDescription);
}
return signatures.GetOrAdd(parameter, _ => new Dictionary<ISet, Signature>(interningEqualityComparer))
.GetOrAdd(result, create);
}
