Added readme for using the NB debugger with FastR.

documentation/Index.md

@@ -5,3 +5,5 @@
 [Limitations](Limitations.md)
 
 [For Developers](dev/Index.md)
+
+[Debugging](debugging.md)

documentation/debugging.md

+# Introduction
+
+Since FastR is implemented atop the Truffle framework, it also supports debugging of applications using NetBeans.
+This is a very convenient and more powerful way for debugging compared to R's browser function.
+
+This section describes how to debug R applications using NetBeans.
+
+# Pre-Requisites
+
+* A recent NetBeans IDE (e.g. nightly build).
+* The _Truffle Debugging Support_ Plugin for NetBeans.  
+  Install this by starting NetBeans and selecting `Tools > Plugins > Available Plugins > Truffle Debugging Support`
+
+# Using the NetBeans Debugger
+
+1. Start NetBeans and install a breakpoint.  
+   Unfortunately, NetBeans does currently not have a suitable R source code editor.  
+   But you can define a breakpoint as you would do for JavaScript.  
+   Open the _Breakpoints_ view: `Window > Debugging > Breakpoints`  
+   Then, create a new breakpoint.  
+   Specify `Debugger: JavaScript` and `Breakpoint Type: Line`.  
+   Enter the path to the R source file in field `File` and the line number for the breakpoint.  
+
+2. Start FastR in debugging mode such that a remote debugger can attach.  
+`bin/R --J @-Xrunjdwp:transport=dt_socket,server=y,suspend=y,address=8000`
+
+3. Run your application.  
+   There are many ways to run your R application. The simplest one is using `source(file.R)`.
+
+# Additional Features
+
+The NetBeans debugger is source-location-based meaning that it assumes every source of an applicates resides somehwere in a source file.  
+However, R applications often run deserialized code or the code is created somehow else.
+
+In order to be still able to use the NetBeans debugger for such source, you first need to generate a temporary source file using a FastR builtin function.
+
+For example, assume we want to debug function `print`, first run following command:  
+	`.fastr.srcinfo(print)`
+
+It will output something similar to  
+	`[1] "/tmp/deparse/print-fca37561e0.r#1"`  
+which is the file containing the deparsed source code of `print`.  
+The generated source file is now associated with function print and a breakpoint can be installed.
+
+# Disclaimer
+
+Since FastR is still in its development phase, debugging may not be possible in all cases.
+