@node Obtaining and Installing Guile
@appendix Obtaining and Installing Guile

Here is the information you will need to get and install Guile and extra
packages and documentation you might need or find interesting.

@menu
* The Basic Guile Package::      
* Packages not shipped with Guile::  
@end menu

@node The Basic Guile Package
@section The Basic Guile Package

Guile can be obtained from the main GNU archive site
@url{ftp://prep.ai.mit.edu/pub/gnu} or any of its mirrors.  The file
will be named guile-version.tar.gz.  The current version is
@value{VERSION}, so the file you should grab is:

@url{ftp://prep.ai.mit.edu/pub/gnu/guile-@value{VERSION}.tar.gz}

To unbundle Guile use the instruction
@example
zcat guile-@value{VERSION}.tar.gz | tar xvf -
@end example
which will create a directory called @file{guile-@value{VERSION}} with
all the sources.  You can look at the file @file{INSTALL} for detailed
instructions on how to build and install Guile, but you should be able
to just do
@example
cd guile-@value{VERSION}
./configure
make install
@end example

This will install the Guile executable @file{guile}, the Guile library
@file{libguile.a} and various associated header files and support
libraries. It will also install the Guile tutorial and reference manual.

@c [[include instructions for getting R4RS]]

Since this manual frequently refers to the Scheme ``standard'', also
known as R4RS, or the
@iftex
``Revised$^4$ Report on the Algorithmic Language Scheme'',
@end iftex
@ifinfo
``Revised^4 Report on the Algorithmic Language Scheme'',
@end ifinfo
we have included the report in the Guile distribution;
@xref{Top, , Introduction, r4rs, Revised(4) Report on the Algorithmic
Language Scheme}.
This will also be installed in your info directory.


@node Packages not shipped with Guile
@section Packages not shipped with Guile

We ship the Guile tutorial and reference manual with the Guile
distribution [FIXME: this is not currently true (Sat Sep 20 14:13:33 MDT
1997), but will be soon.]  Since the Scheme standard (R4RS) is a stable
document, we ship that too.

Here are references (usually World Wide Web URLs) to some other freely
redistributable documents and packages which you might find useful if
you are using Guile.

@table @strong
@item SCSH
the Scheme Shell.  Gary Houston has ported SCSH to Guile.  The relevant
chapter (@pxref{The Scheme shell (scsh)}) has references to the SCSH web
page with all its documentation.

@item SLIB
a portable Scheme library maintained by Aubrey Jaffer.  SLIB can be
obtained by ftp from @url{ftp://prep.ai.mit.edu/pub/gnu/jacal/}.

The SLIB package should be unpacked somewhere in Guile's load path.  It
will typically be unpacked in @file{/usr/local/share/guile/site}, so
that it will be @file{/usr/local/share/guile/site/slib}.

Guile might have been installed with a different prefix, in which case
the load path can be checked from inside the interpreter with:

@smalllisp
guile> %load-path
("/usr/local/share/guile/site" "/usr/local/share/guile/1.3a" "/usr/local/share/guile" ".")
@end smalllisp

The relevant chapter (@pxref{SLIB}) has details on how to use SLIB with
Guile.

@item JACAL
a symbolic math package by Aubrey Jaffer.  The latest version of Jacal
can be obtained from @url{ftp://prep.ai.mit.edu/pub/gnu/jacal/}, and
should be unpacked in @file{/usr/local/share/guile/site/slib} so that
it will be in @file{/usr/local/share/guile/site/slib/jacal}.

The relevant section (@pxref{JACAL}) has details on how to use Jacal.
@end table


@page
@node Debugger User Interface
@appendix Debugger User Interface
 
@c      --- The title and introduction of this appendix need to
@c          distinguish this clearly from the chapter on the internal
@c          debugging interface.
 
When debugging a program, programmers often find it helpful to examine
the program's internal status while it runs: the values of internal
variables, the choices made in @code{if} and @code{cond} statements, and
so forth.  Guile Scheme provides a debugging interface that programmers
can use to single-step through Scheme functions and examine symbol
bindings.  This is different from the @ref{Debugging}, which permits
programmers to debug the Guile interpreter itself.  Most programmers
will be more interested in debugging their own Scheme programs than the
interpreter which evaluates them.
 
[FIXME: should we include examples of traditional debuggers
and explain why they can't be used to debug interpreted Scheme or Lisp?]
 
@menu
* Single-Step::         Execute a program or function one step at a time.
* Trace::               Print a report each time a given function is called.
* Backtrace::           See a list of the statements that caused an error.
* Stacks and Frames::	Examine the state of an interrupted program.
@end menu
 
@node Single-Step
@appendixsec Single-Step
 
@node Trace
@appendixsec Trace

When a function is @dfn{traced}, it means that every call to that
function is reported to the user during a program run.  This can help a
programmer determine whether a function is being called at the wrong
time or with the wrong set of arguments.

@defun trace function
Enable debug tracing on @code{function}.  While a program is being run, Guile
will print a brief report at each call to a traced function,
advising the user which function was called and the arguments that were
passed to it.
@end defun

@defun untrace function
Disable debug tracing for @code{function}.
@end defun

Example:

@lisp
(define (rev ls)
  (if (null? ls)
      '()
      (append (rev (cdr ls))
              (cons (car ls) '())))) @result{} rev

(trace rev) @result{} (rev)

(rev '(a b c d e))
@result{} [rev (a b c d e)]
   |  [rev (b c d e)]
   |  |  [rev (c d e)]
   |  |  |  [rev (d e)]
   |  |  |  |  [rev (e)]
   |  |  |  |  |  [rev ()]
   |  |  |  |  |  ()
   |  |  |  |  (e)
   |  |  |  (e d)
   |  |  (e d c)
   |  (e d c b)
   (e d c b a)
   (e d c b a)
@end lisp
 
Note the way Guile indents the output, illustrating the depth of
execution at each function call.  This can be used to demonstrate, for
example, that Guile implements self-tail-recursion properly:
 
@lisp
(define (rev ls sl)
  (if (null? ls)
      sl
      (rev (cdr ls)
           (cons (car ls) sl)))) @result{} rev
 
(trace rev) @result{} (rev)
 
(rev '(a b c d e) '())
@result{} [rev (a b c d e) ()]
   [rev (b c d e) (a)]
   [rev (c d e) (b a)]
   [rev (d e) (c b a)]
   [rev (e) (d c b a)]
   [rev () (e d c b a)]
   (e d c b a)
   (e d c b a)
@end lisp
 
Since the tail call is effectively optimized to a @code{goto} statement,
there is no need for Guile to create a new stack frame for each
iteration.  Using @code{trace} here helps us see why this is so.
 
@node Backtrace
@appendixsec Backtrace

@node Stacks and Frames
@appendixsec Stacks and Frames

When a running program is interrupted, usually upon reaching an error or
breakpoint, its state is represented by a @dfn{stack} of suspended
function calls, each of which is called a @dfn{frame}.  The programmer
can learn more about the program's state at the point of interruption by
inspecting and modifying these frames.

@deffn primitive stack? obj
Return @code{#t} if @var{obj} is a calling stack.
@end deffn

@deffn primitive make-stack
@end deffn

@deffn syntax start-stack id exp
Evaluate @var{exp} on a new calling stack with identity @var{id}.  If
@var{exp} is interrupted during evaluation, backtraces will not display
frames farther back than @var{exp}'s top-level form.  This macro is a
way of artificially limiting backtraces and stack procedures, largely as
a convenience to the user.
@end deffn

@deffn primitive stack-id stack
Return the identifier given to @var{stack} by @code{start-stack}.
@end deffn

@deffn primitive stack-ref
@end deffn

@deffn primitive stack-length
@end deffn

@deffn primitive frame?
@end deffn

@deffn primitive last-stack-frame
@end deffn

@deffn primitive frame-number
@end deffn

@deffn primitive frame-source
@end deffn

@deffn primitive frame-procedure
@end deffn

@deffn primitive frame-arguments
@end deffn

@deffn primitive frame-previous
@end deffn

@deffn primitive frame-next
@end deffn

@deffn primitive frame-real?
@end deffn

@deffn primitive frame-procedure?
@end deffn

@deffn primitive frame-evaluating-args?
@end deffn

@deffn primitive frame-overflow
@end deffn