が早{はや}いか
and や否{いな}や
both seem to mean "as soon as". They describe a relation between two actions, where one action occurs when another does.
I'm a little fuzzy on the difference, though. I think, from reading examples in my N1 practise book that が早{はや}いか
is more momentary. Action A is something that is more or less instantaneous, triggering B to happen in a mere moment.
や否{いな}や
, on the other hand, can be a little more overlapping. While action A is in the process of completing, B happens.
Here are some example sentences which seem to support that difference:
時計{とけい}が10時{じ}を告{つ}げるが早いか、いっせいに問{と}い合{あ}わせの電話{でんわ}が鳴{な}り出{だ}した。
The clock hitting ten is an instantaneous occurrence.
母{はは}の足音{あしおと}が聞{き}こえるや否{いな}や、愛犬{いあけん}のチロは玄関{げんかん}までダッシュした。
Footsteps continue over a small amount of time, so there is a bit of overlap between them being heard by the dog, and it running toward the front door.
However, this example sentence doesn't fit the mould:
電車{でんしゃ}のドアが開{ひら}くや否{いな}や、どっと乗客{じょうかきゃく}が降{お}りてきた。
A train door opening, to me, seems more of an instantaneous occurrence than not. Though maybe that's just my take on it. I could see how some might argue that it is a point in time more than a section of time.
Am I correct in that they a differentiated by how instantaneous event A is? Is there anything else that differentiates them?