I think same sex repels where as opposite sex attracts undermining the views of homo-segxwal. Thus, i guest the babes here should rub minds together and come out with their yardsticks but i know one man's food is another man's poison. hence, the criteria is subjective to individuals in question..

it is artificial and unrealistic. while not remain calm and patient till the storm of absence is over

sex is not all and all in relationship. if so one has relegated himself or herself animal instinct but man is a rational animal implying thus in friendship, sex is only secondary and not primary. otherwise, the opposite sex simply act as a sex machine which is not the central focus on friendship.