78 lines
1.8 KiB
Scheme
78 lines
1.8 KiB
Scheme
; -*- Mode: Scheme; Syntax: Scheme; Package: Scheme; -*-
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; Copyright (c) 1993-1999 by Richard Kelsey and Jonathan Rees. See file COPYING.
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; This is file condition.scm.
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;;;; Condition hierarchy
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; General design copied from gnu emacs.
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(define *condition-types* '())
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(define (condition-supertypes type)
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(assq type *condition-types*))
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(define (define-condition-type type supertypes)
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(set! *condition-types*
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(cons (cons type (apply append
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(map (lambda (sup)
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(or (condition-supertypes sup)
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(error "unrecognized condition type"
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sup)))
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supertypes)))
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*condition-types*)))
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(define (condition-predicate name)
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(lambda (c)
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(and (pair? c)
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(let ((probe (condition-supertypes (car c))))
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(if probe
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(if (memq name probe) #t #f)
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#f)))))
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(define (condition? x)
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(and (pair? x)
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(list? x)
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(condition-supertypes (car x))))
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(define condition-type car)
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(define condition-stuff cdr)
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; Errors
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(define-condition-type 'error '())
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(define error? (condition-predicate 'error))
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(define-condition-type 'call-error '(error))
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(define call-error? (condition-predicate 'call-error))
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(define-condition-type 'read-error '(error))
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(define read-error? (condition-predicate 'read-error))
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; Exceptions
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(define-condition-type 'exception '(error))
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(define exception? (condition-predicate 'exception))
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(define exception-opcode cadr)
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(define exception-reason caddr)
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(define exception-arguments cdddr)
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(define (make-exception opcode reason args)
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(make-condition 'exception (cons opcode (cons reason args))))
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; Warnings
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(define-condition-type 'warning '())
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(define warning? (condition-predicate 'warning))
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(define-condition-type 'syntax-error '(warning))
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(define syntax-error? (condition-predicate 'syntax-error))
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; Interrupts
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(define-condition-type 'interrupt '())
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(define interrupt? (condition-predicate 'interrupt))
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