static public bool NotContain <T, TEq>(this StrI1 <T> str, T x, TEq eq)
where TEq : IEqualityComparer <T>
{
return(!str.Contain(x, eq));
}
static public bool Contain_eqDefault <T, TEq>(this StrI1 <T> str, T x)
where TEq : IEqualityComparer <T>, new()
{
return(str.Contain(x, SingletonByDefault <TEq> .Instance));
}