I read many times this question but I'm still confused about the differences between these two grammars. The first answer says that
〜ていない has a possible third meaning not used, "I eat my meal and I am here (/I exist)" that is "a terrible way to read it", and when it goes to explain
〜ないでいる, it means "I am here (/I exist) without eating my meal." which seems very similar to the terrible way of reading it.
ていない mean "... and I'm not here"?
I appreciate the efforts of the person who answered, but I really didn't understand it, especially what "instrumental adjunct" is.
I'm not sure, but the difference between them seems to be how long the state remains.
食べていない I don't eat something since a long time ago, it remains until now and it will remain in the future,
食べないでいる on the other hand, would mean that I'm in the state of not eating now, but that won't last too long.
The sentence that made me search about this grammar is:
僕が…書けないでいるから？ It's an answer from person A to person B when asked why the person A is in the same place as B.
Could someone explain the differences between these two grammars and when should I use it?