--- /dev/null
+;;; srfi-34.scm --- Exception handling for programs
+
+;; Copyright (C) 2003, 2006, 2008 Free Software Foundation, Inc.
+;;
+;; This library is free software; you can redistribute it and/or
+;; modify it under the terms of the GNU Lesser General Public
+;; License as published by the Free Software Foundation; either
+;; version 2.1 of the License, or (at your option) any later version.
+;;
+;; This library is distributed in the hope that it will be useful,
+;; but WITHOUT ANY WARRANTY; without even the implied warranty of
+;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+;; Lesser General Public License for more details.
+;;
+;; You should have received a copy of the GNU Lesser General Public
+;; License along with this library; if not, write to the Free Software
+;; Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+
+;;; Author: Neil Jerram <neil@ossau.uklinux.net>
+
+;;; Commentary:
+
+;; This is an implementation of SRFI-34: Exception Handling for
+;; Programs. For documentation please see the SRFI-34 document; this
+;; module is not yet documented at all in the Guile manual.
+
+;;; Code:
+
+(define-module (srfi srfi-34)
+ #:export (with-exception-handler
+ raise)
+ #:export-syntax (guard))
+
+(cond-expand-provide (current-module) '(srfi-34))
+
+(define throw-key 'srfi-34)
+
+(define (with-exception-handler handler thunk)
+ "Returns the result(s) of invoking THUNK. HANDLER must be a
+procedure that accepts one argument. It is installed as the current
+exception handler for the dynamic extent (as determined by
+dynamic-wind) of the invocation of THUNK."
+ (with-throw-handler throw-key
+ thunk
+ (lambda (key obj)
+ (handler obj))))
+
+(define (raise obj)
+ "Invokes the current exception handler on OBJ. The handler is
+called in the dynamic environment of the call to raise, except that
+the current exception handler is that in place for the call to
+with-exception-handler that installed the handler being called. The
+handler's continuation is otherwise unspecified."
+ (throw throw-key obj))
+
+(define-macro (guard var+clauses . body)
+ "Syntax: (guard (<var> <clause1> <clause2> ...) <body>)
+Each <clause> should have the same form as a `cond' clause.
+
+Semantics: Evaluating a guard form evaluates <body> with an exception
+handler that binds the raised object to <var> and within the scope of
+that binding evaluates the clauses as if they were the clauses of a
+cond expression. That implicit cond expression is evaluated with the
+continuation and dynamic environment of the guard expression. If
+every <clause>'s <test> evaluates to false and there is no else
+clause, then raise is re-invoked on the raised object within the
+dynamic environment of the original call to raise except that the
+current exception handler is that of the guard expression."
+ (let ((var (car var+clauses))
+ (clauses (cdr var+clauses)))
+ `(catch ',throw-key
+ (lambda ()
+ ,@body)
+ (lambda (key ,var)
+ (cond ,@(if (eq? (caar (last-pair clauses)) 'else)
+ clauses
+ (append clauses
+ `((else (throw key ,var))))))))))
+
+;;; (srfi srfi-34) ends here.
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