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- ;;; exceptions.scm --- The R6RS exceptions library
- ;; Copyright (C) 2010, 2011 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 3 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
- (library (rnrs exceptions (6))
- (export guard with-exception-handler raise raise-continuable)
- (import (rnrs base (6))
- (rnrs control (6))
- (rnrs conditions (6))
- (rnrs records procedural (6))
- (rnrs records inspection (6))
- (only (guile)
- format
- newline
- display
- filter
- set-exception-printer!
- with-throw-handler
- *unspecified*
- @@))
- (define raise (@@ (rnrs records procedural) r6rs-raise))
- (define raise-continuable
- (@@ (rnrs records procedural) r6rs-raise-continuable))
- (define raise-object-wrapper?
- (@@ (rnrs records procedural) raise-object-wrapper?))
- (define raise-object-wrapper-obj
- (@@ (rnrs records procedural) raise-object-wrapper-obj))
- (define raise-object-wrapper-continuation
- (@@ (rnrs records procedural) raise-object-wrapper-continuation))
- (define (with-exception-handler handler thunk)
- (with-throw-handler 'r6rs:exception
- thunk
- (lambda (key . args)
- (if (and (not (null? args))
- (raise-object-wrapper? (car args)))
- (let* ((cargs (car args))
- (obj (raise-object-wrapper-obj cargs))
- (continuation (raise-object-wrapper-continuation cargs))
- (handler-return (handler obj)))
- (if continuation
- (continuation handler-return)
- (raise (make-non-continuable-violation))))
- *unspecified*))))
- (define-syntax guard0
- (syntax-rules ()
- ((_ (variable cond-clause ...) . body)
- (call/cc (lambda (continuation)
- (with-exception-handler
- (lambda (variable)
- (continuation (cond cond-clause ...)))
- (lambda () . body)))))))
- (define-syntax guard
- (syntax-rules (else)
- ((_ (variable cond-clause ... . ((else else-clause ...))) . body)
- (guard0 (variable cond-clause ... (else else-clause ...)) . body))
- ((_ (variable cond-clause ...) . body)
- (guard0 (variable cond-clause ... (else (raise variable))) . body))))
- ;;; Exception printing
- (define (exception-printer port key args punt)
- (cond ((and (= 1 (length args))
- (raise-object-wrapper? (car args)))
- (let ((obj (raise-object-wrapper-obj (car args))))
- (cond ((condition? obj)
- (display "ERROR: R6RS exception:\n" port)
- (format-condition port obj))
- (else
- (format port "ERROR: R6RS exception: `~s'" obj)))))
- (else
- (punt))))
- (define (format-condition port condition)
- (let ((components (simple-conditions condition)))
- (if (null? components)
- (format port "Empty condition object")
- (let loop ((i 1) (components components))
- (cond ((pair? components)
- (format port " ~a. " i)
- (format-simple-condition port (car components))
- (when (pair? (cdr components))
- (newline port))
- (loop (+ i 1) (cdr components))))))))
- (define (format-simple-condition port condition)
- (define (print-rtd-fields rtd field-names)
- (let ((n-fields (vector-length field-names)))
- (do ((i 0 (+ i 1)))
- ((>= i n-fields))
- (format port " ~a: ~s"
- (vector-ref field-names i)
- ((record-accessor rtd i) condition))
- (unless (= i (- n-fields 1))
- (newline port)))))
- (let ((condition-name (record-type-name (record-rtd condition))))
- (let loop ((rtd (record-rtd condition))
- (rtd.fields-list '())
- (n-fields 0))
- (cond (rtd
- (let ((field-names (record-type-field-names rtd)))
- (loop (record-type-parent rtd)
- (cons (cons rtd field-names) rtd.fields-list)
- (+ n-fields (vector-length field-names)))))
- (else
- (let ((rtd.fields-list
- (filter (lambda (rtd.fields)
- (not (zero? (vector-length (cdr rtd.fields)))))
- (reverse rtd.fields-list))))
- (case n-fields
- ((0) (format port "~a" condition-name))
- ((1) (format port "~a: ~s"
- condition-name
- ((record-accessor (caar rtd.fields-list) 0)
- condition)))
- (else
- (format port "~a:\n" condition-name)
- (let loop ((lst rtd.fields-list))
- (when (pair? lst)
- (let ((rtd.fields (car lst)))
- (print-rtd-fields (car rtd.fields) (cdr rtd.fields))
- (when (pair? (cdr lst))
- (newline port))
- (loop (cdr lst)))))))))))))
- (set-exception-printer! 'r6rs:exception exception-printer)
- )
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