I was reading a book and I noticed a strange sentence for me. "It was brave of you to help Arthur - and you a stranger". What does "you a stranger" mean? Is it a shortened "you are a stranger"?
There is a missing but implied verb. You have the correct verb, but wrong tense.
"It was brave of you to help Arthur - and you [being] a stranger."
For full clarity, what the speaker is actually saying is:
"It was brave of you to help Arthur - and [even more brave with] you [being] a stranger [to him]."
" A stranger " is a complement of " you " and together they an extension of the main sentence with a reinforcement of "help" from unexpected quarters.
To make it simple, we know verbs as well as prepositions take objects and when those objects are not complete by themselves, they take complements. Let me take the liberty to rewrite your sentence:
- It was brave of you a stranger to help Arthur!
That completes the intended meaning but the tag in your sentence gains in intensity. However one may be inclined to call " a stranger " an appositive. But as it has no coma before ( , ) I'll go with the objective complement explanation.
They were explaining to the person how kind they were to help even though they were a stranger. As most strangers would choose not to help and go on with their day.
"You a stranger" is a quicker way of saying "You're a stranger", in most books (especially older books) if the character is of African descent/ black, they are usually talking in Ebonics, or slang.