module/ice-9/stack-catch.scm

   1 ;;; installed-scm-file
   2
   3 ;;;;    Copyright (C) 2001, 2006, 2010 Free Software Foundation, Inc.
   4 ;;;;
   5 ;;;; This library is free software; you can redistribute it and/or
   6 ;;;; modify it under the terms of the GNU Lesser General Public
   7 ;;;; License as published by the Free Software Foundation; either
   8 ;;;; version 3 of the License, or (at your option) any later version.
   9 ;;;;
  10 ;;;; This library is distributed in the hope that it will be useful,
  11 ;;;; but WITHOUT ANY WARRANTY; without even the implied warranty of
  12 ;;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13 ;;;; Lesser General Public License for more details.
  14 ;;;;
  15 ;;;; You should have received a copy of the GNU Lesser General Public
  16 ;;;; License along with this library; if not, write to the Free Software
  17 ;;;; Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  18 ;;;;
  19
  20 (define-module (ice-9 stack-catch)
  21   #:use-module (ice-9 save-stack)
  22   #:export (stack-catch))
  23
  24 (define (stack-catch key thunk handler)
  25   "Like @code{catch}, invoke @var{thunk} in the dynamic context of
  26 @var{handler} for exceptions matching @var{key}, but also save the
  27 current stack state in the @var{the-last-stack} fluid, for the purpose
  28 of debugging or re-throwing of an error.  If thunk throws to the
  29 symbol @var{key}, then @var{handler} is invoked this way:\n
  30 @example
  31  (handler key args ...)
  32 @end example\n
  33 @var{key} is a symbol or #t.\n
  34 @var{thunk} takes no arguments.  If @var{thunk} returns normally, that
  35 is the return value of @code{catch}.\n
  36 Handler is invoked outside the scope of its own @code{catch}.  If
  37 @var{handler} again throws to the same key, a new handler from further
  38 up the call chain is invoked.\n
  39 If the key is @code{#t}, then a throw to @emph{any} symbol will match
  40 this call to @code{catch}."
  41   (catch key
  42          thunk
  43          handler
  44          (lambda (key . args)
  45            ;; Narrow by two more frames: this one, and the throw handler.
  46            (save-stack 2)
  47            (apply throw key args))))