list/ob-R.el (org-babel-R-command-primary-prompt,
org-babel-R-evaluate-session): Former adds customizable prompt value
the latter utilizes it.

My R prompt looks like this "ℝ> ".  Babel needs to know more how to
handle various situations so the
regex used in `org-babel-R-evaluate-session' to identify the prompt
looks like this "^\\([ ]*[ℝ>+\\.][ ]?\\)+\\([[0-9]+\\|[ ]\\)".
It is required to handle various R prompt situations correctly.  It
may change over time to handle more situations.  The
user doesn't need to know about those details.  The user only cares
about the R prompt alone.  For example, when
they set the prompt in R it looks like this =options(prompt="ℝ> ")=,
it is very simple.  It should be this simple for bable, too.

This change adds a user customizable variable for the prompt from user
perspective `org-babel-R-command-primary-prompt'.  That variable is
utilized in `org-babel-R-evaluate-session' where the full regular
expression to match the prompt is constructed.  This makes it very
easy to handle a custom prompt since from the R side of things, the
value of `org-babel-R-command-primary-prompt' is the only thing that
the user needs to know to set.  Via custom it looks like this
'(org-babel-R-command-primary-prompt "ℝ>").

TINYCHANGE
---
 lisp/ob-R.el | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/lisp/ob-R.el b/lisp/ob-R.el
index 41b943c..1cb675b 100644
--- a/lisp/ob-R.el
+++ b/lisp/ob-R.el
@@ -87,6 +87,11 @@ this variable.")
   :version "24.1"
   :type 'string)

+(defcustom org-babel-R-command-primary-prompt ">"
+  "User configurable portion of the primary prompt."
+  :group 'org-babel
+  :type 'string)
+
 (defvar ess-local-process-name) ; dynamically scoped
 (defun org-babel-edit-prep:R (info)
   (let ((session (cdr (assoc :session (nth 2 info)))))
@@ -413,6 +418,7 @@ last statement in BODY, as elisp."
     (list body org-babel-R-eoe-indicator)
     "\n"))
  (inferior-ess-send-input)))))) "\n"))))
+                      (concat  "^\\([ ]*["
org-babel-R-command-primary-prompt "+\\.][ ]?\\)+\\([[0-9]+\\|[ ]\\)")
line)

 (defun org-babel-R-process-value-result (result column-names-p)
   "R-specific processing of return value.
--
1.9.2