40 lines
1.3 KiB
Scheme
40 lines
1.3 KiB
Scheme
#lang scheme/load
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;; purpose: when on-tick or on-xxx has been redefined,
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;; --- raise more specific error message
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;; (why am I running this in scheme/load for the namespace in eval)
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(error-print-source-location #f)
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(define legal "~a: not a legal clause in a world description")
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(define double
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(string-append (format legal 'on-tick) ", on-tick has been redefined"))
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(with-handlers ((exn:fail:syntax?
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(lambda (x)
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(unless (string=? (exn-message x) double) (raise x)))))
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(eval '(module a scheme
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(require 2htdp/universe)
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(local ((define (run) (big-bang 0 (on-tick on-tick)))
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(define (on-tick t) 0))
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10))))
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;; purpose: catch illegal shapes of the form (kwd . stuff)
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(with-handlers ((exn:fail:syntax?
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(lambda (e)
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(unless (string=? (exn-message e) (format legal 'on-tic))
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(raise e)))))
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(eval '(module a scheme
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(require 2htdp/universe)
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(big-bang 0 (on-tic add1)))))
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;; purpose: catch illegal atomic clauses
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(with-handlers ((exn:fail:syntax?
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(lambda (e)
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(unless (string=? (exn-message e) (format legal 'stop-when))
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(raise e)))))
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(eval '(module a scheme
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(require 2htdp/universe)
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(big-bang 0 (on-tick add1) stop-when)))) |