/// <summary>
/// Appends a pattern that matches a character from a specified base group except characters from a specified excluded group.
/// </summary>
/// <param name="baseGroup">A base group.</param>
/// <param name="excludedGroup">An excluded group.</param>
/// <exception cref="ArgumentNullException"><paramref name="baseGroup"/> or <paramref name="excludedGroup"/> is <c>null</c>.</exception>
public void AppendSubtraction(IBaseGroup baseGroup, IExcludedGroup excludedGroup)
{
if (baseGroup == null)
throw new ArgumentNullException(nameof(baseGroup));
if (excludedGroup == null)
throw new ArgumentNullException(nameof(excludedGroup));
AppendCharGroupStart();
baseGroup.AppendBaseGroupTo(this);
AppendDirect('-');
excludedGroup.AppendExcludedGroupTo(this);
AppendCharGroupEnd();
}
