/// <summary>
/// Safely retrieves the number of classes that the Bayes point machine classifier is used for.
/// </summary>
/// <typeparam name="TInstanceSource">The type of the instance source.</typeparam>
/// <typeparam name="TInstance">The type of an instance.</typeparam>
/// <typeparam name="TLabelSource">The type of the label source.</typeparam>
/// <typeparam name="TLabel">The type of a label.</typeparam>
/// <param name="mapping">The mapping.</param>
/// <param name="instanceSource">An optional instance source.</param>
/// <param name="labelSource">An optional label source.</param>
/// <returns>The number of classes that the Bayes point machine classifier is used for.</returns>
/// <exception cref="MappingException">Thrown if there are less than three classes.</exception>
public static int GetClassCountSafe <TInstanceSource, TInstance, TLabelSource, TLabel>(
this IBayesPointMachineClassifierMapping <TInstanceSource, TInstance, TLabelSource, TLabel> mapping,
TInstanceSource instanceSource = default(TInstanceSource),
TLabelSource labelSource = default(TLabelSource))
{
int classCount = mapping.GetClassCount(instanceSource, labelSource);
if (classCount < 2)
{
throw new MappingException("There must be at least two classes.");
}
return(classCount);
}
