r6rs docs in the manual

* doc/ref/r6rs.texi (R6RS Support): Skeleton of docs on our R6RS
  support.

* doc/ref/guile.texi:
* doc/ref/Makefile.am: Add r6rs.texi.

* doc/ref/intro.texi: Add a link to r6rs.texi.

doc/ref/Makefile.am

@@ -69,6 +69,7 @@ guile_TEXINFOS = preface.texi			\
 		 data-rep.texi			\
 		 repl-modules.texi		\
 		 srfi-modules.texi		\
+		 r6rs.texi			\
 		 misc-modules.texi		\
 		 api-compound.texi		\
 		 autoconf.texi			\

doc/ref/guile.texi

@@ -350,6 +350,7 @@ available through both Scheme and C interfaces.
 * POSIX::                       POSIX system calls and networking.
 * getopt-long::                 Command line handling.
 * SRFI Support::                Support for various SRFIs.
+* R6RS Support::                Modules defined by the R6RS.
 * Readline Support::            Module for using the readline library.
 * Value History::               Maintaining a value history in the REPL.
 * Pretty Printing::             Nicely formatting Scheme objects for output.
@@ -368,6 +369,7 @@ available through both Scheme and C interfaces.
 @include posix.texi
 @include mod-getopt-long.texi
 @include srfi-modules.texi
+@include r6rs.texi
 @include repl-modules.texi
 @include misc-modules.texi
 @include expect.texi

doc/ref/intro.texi

@@ -78,7 +78,7 @@ implementations -- including Guile -- have previously done in
 different ways.  Guile has been updated to incorporate some of the
 features of R6RS, and to adjust some existing features to conform to
 the R6RS specification, but it is by no means a complete R6RS
-implementation.
+implementation. @xref{R6RS Support}.
 
 Between R5RS and R6RS, the SRFI process (@url{http://srfi.schemers.org/})
 standardised interfaces for many practical needs, such as multithreaded

doc/ref/r6rs.texi

@@ -0,0 +1,131 @@
+@c -*-texinfo-*-
+@c This is part of the GNU Guile Reference Manual.
+@c Copyright (C)  2010
+@c   Free Software Foundation, Inc.
+@c See the file guile.texi for copying conditions.
+
+@node R6RS Support
+@section R6RS Support
+@cindex R6RS
+
+@xref{R6RS Libraries}, for more information on how to define R6RS libraries, and
+their integration with Guile modules.
+
+@menu
+* R6RS Incompatibilities::              Guile mostly implements R6RS.
+* R6RS Standard Libraries::             Modules defined by the R6RS.
+@end menu
+
+@node R6RS Incompatibilities
+@subsection Incompatibilities with the R6RS
+
+There are some incompatibilities between Guile and the R6RS. Some of them are
+intentional, some of them are bugs, and some are simply unimplemented features.
+Please let the Guile developers know if you find one that is not on this list.
+
+@itemize
+@item
+In the R6RS, internal definitions expand to @code{letrec*}, not @code{letrec}.
+Guile does not support @code{letrec*}, though that would be nice.
+
+@item
+The R6RS specifies many situations in which a conforming implementation must
+signal a specific error. Guile doesn't really care about that too much -- if a
+correct R6RS program would not hit that error, we don't bother checking for it.
+
+@item
+Multiple @code{library} forms in one file are not yet supported. This is because
+the expansion of @code{library} sets the current module, but does not restore
+it. This is a bug.
+@end itemize
+
+
+@node R6RS Standard Libraries
+@subsection R6RS Standard Libraries
+
+The R6RS standard defines a core language and a number of standard libraries.
+Here we briefly list the libraries that have been implemented for Guile.
+
+All of these libraries are available as Guile modules, for use in standard Guile
+code, via @code{use-modules}, or for use in portable R6RS code, via the
+@code{library} and @code{import} forms. @xref{R6RS Libraries}, for more
+information.
+
+We do not attempt to document these libraries fully here, as most of their
+functionality is already available in Guile itself. The expectation is that most
+Guile users will use the well-known and well-documented Guile modules. These
+R6RS libraries are mostly useful to users who want to port their code to other
+R6RS systems, in which case a copy of the R6RS report itself is necessary. It
+may be found at the R6RS web page, @url{http://r6rs.org/}.
+
+First, there is the base library, defined in the base R6RS report:
+
+@example
+(use-modules (rnrs base))
+@end example
+
+One may also import it to the current module using the R6RS @code{import} form:
+
+@example
+(import (rnrs base))
+@end example
+
+All of the @code{rnrs} modules have the version of @code{(6)}, which may be
+specified when importing the module:
+
+@example
+(import (rnrs base (6)))
+(use-modules ((rnrs base) #:version (6)))
+@end example
+
+@xref{R6RS Version References}, for more information on versions.
+
+Next there is a set of libraries that collectively form the @code{(rnrs)}
+composite library. The following statements are equivalent:
+
+@example
+(import (rnrs))
+
+(use-modules (rnrs))
+
+(import (rnrs arithmetic bitwise (6))
+        (rnrs arithmetic fixnums (6))
+        (rnrs arithmetic flonums (6))
+        (rnrs base (6))
+        (rnrs bytevectors)
+        (rnrs conditions (6))
+        (rnrs control (6))
+        (rnrs enums (6))
+        (rnrs exceptions (6))
+        (rnrs files (6))
+        (rnrs hashtables (6))
+        (rnrs io ports)
+        (rnrs io simple (6))
+        (rnrs lists (6))
+        (rnrs programs (6))
+        (rnrs records inspection (6))
+        (rnrs records procedural (6))
+        (rnrs records syntactic (6))
+        (rnrs sorting (6))
+        (rnrs syntax-case (6)))
+@end example
+
+Finally there are a number of modules that the @code{(rnrs)} module does not
+re-export:
+
+@example
+(import (rnrs mutable-pairs (6))
+        (rnrs mutable-strings (6))
+        (rnrs r5rs (6))
+        (rnrs eval (6))
+        (rnrs unicode (6)))
+@end example
+
+See the R6RS Standard Libraries specification, for more information on these
+modules.
+
+@c r6rs.texi ends here
+
+@c Local Variables:
+@c TeX-master: "guile.texi"
+@c End: