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Re: [MIT-Scheme-devel] [commit 9ddb22a] Fix nasty bug: modifying a hash
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From: |
Taylor R Campbell |
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Subject: |
Re: [MIT-Scheme-devel] [commit 9ddb22a] Fix nasty bug: modifying a hash table could scramble its buckets. |
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Date: |
Fri, 17 Mar 2017 06:50:51 +0000 |
> Date: Tue Feb 7 20:23:41 2017 -0800
> From: Chris Hanson <org/chris-hanson/cph>
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> Fix nasty bug: modifying a hash table could scramble its buckets.
This was intentional -- as the documentation notes, the procedure
passed to HASH-TABLE/MODIFY! is not allowed to use the hash table.
In contrast, SRFI 69 HASH-TABLE-UPDATE! does allow the procedure you
pass to use the table arbitrarily.
Note that even with your change, you can still screw yourself by,
e.g., removing the entry and re-entering it inside the procedure. See
test-hash-table.scm for several screw cases that HASH-TABLE-UPDATE!
goes to the extra effort to avoid.
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Taylor R Campbell <=