Difference of using Will, Going to, Doing to

INSTANT DECISION - a promise, a threat (угроза), a prediction, an opinion, a reaction to a stimulus - an on-the-spot decision / a solution = an offer / a suggestion

BE GOING TO - a personal intention, a professional forecast, an inevitable event or action resulting from what is going on now = commentary

BE DOING + when - an arrangement, a contract, 2+ participants

EXAMPLE:

What will you do tonight? (high probability - c высокой долей вероятности будете)

What are you going to do tonight? (намереватесь - intend)

What are you doing tonight? (точно делать будете - есть договорённость с третьими лицами / an arrangement)


WILL vs GOING TO

PLANS

+ private = PRESENT CONTINUOUS arrangements
+ public = PRESENT SIMPLE timetable, a TV guide, shop opening and closing times, departure and arrival times, concerts, events, etc