[ESS] Eval region line by line

[Ghislain Vieilledent]

Dear ESS-GNU/Emacs users,

I would have two questions (which are linked):

1- With "C-c C-r", it is possible to evaluate a region. Nevertheless,
the whole region is evaluated at the same time and the result is
displayed in a block in the *R* buffer. I would prefer a line-by-line
evaluation (for all the selected region), with results appearing step by
step in the *R* buffer. How can I modified my .emacs to obtain this? 

2- When I have long regions of code to evaluate, my "script.r" buffer
can't be written until the evaluation of the whole region has been done.
How can I release the script.r buffer to modified it while selected
region is being evaluated?

Thanks for your help,

Ghislain Vieilledent