"We went out for dinner
. When I had finished eating, I saw a poor man walking on the street."
present prog.
" I am reading
while my sister is watching."
past prog.
" I was reading
while my sister was watching"
future prog. is this possible?
" I will be reading while my sister will be watching when you arrive tomorrow morning"
::
correct (same meaning):
I will be reading
and my sister will be watching when you arrive.
correct (different meaning, using
while in future tense):
I will be reading and my sister will be watching
while you are on your way here / travelling towards us / etc.
In the first two sentences which you wrote, there are two seperate, progressive subjects, and 'while' tells us that they are simultaneous.
In the last sentence you wrote, 'when' denotes the timeframe of the sentence, so 'while' cannot refer to the timeframe, and its meaning changes (see below). When referring to time, 'while' must connect two things that are both happen
ing, whereas "when you come home" is not in progressive tense. To use 'while' reffering to future progressives happening simultaneously, you must replace 'when' with 'while' and change the action referred to by 'when' into a progressive action.
BE CAREFUL!
'while' is sometimes (usually informally) used as 'whereas.'
eg: "I will be reading
, while my sister will be watching" == "I will be reading, whereas my sister will be watching."
-=and=-
"While I will be reading, my sister will be watching" == "Whereas I will be reading, my sister will be watching."
You could even say: "I will be reading,
but my sister will be watching when you come home."
I hope that helps!
Jesse
tenses 
Linear Mode
