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bug#48315: (ice-9 match) does not suport #nil
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From: |
Taylan Kammer |
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Subject: |
bug#48315: (ice-9 match) does not suport #nil |
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Date: |
Wed, 12 May 2021 22:03:57 +0200 |
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User-agent: |
Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.10.1 |
This was mind-boggling to debug!
In syntax-rules, the pattern (x ...) will match #nil, since it
matches the empty list. This can have surprising consequences.
Consider:
(define-syntax test
(syntax-rules ()
((test (x ...))
(x ...))
((test x)
x)))
(test (+ 1 2)) ; => 3
(test 123) ; => 123
(test #f) ; => #f
;; However...
(test #nil) ; error
Anyway, attached is a patch to fix the issue in match.
- Taylan
0001-Fix-match-when-used-directly-on-the-nil-constant.patch
Description: Text document