public override int CompareTo(object obj)
{
if (obj == null)
{
return(1);
}
SingleProposition other = obj as SingleProposition;
return(this.Letter.CompareTo(other.Letter));
}
// override object.Equals
public override bool Equals(object obj)
{
if (obj == null || GetType() != obj.GetType())
{
return(false);
}
SingleProposition other = obj as SingleProposition;
return(other.Letter.Equals(this.Letter));
}