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Re: association list bug? -- version 1.6.4
From: |
Kevin Ryde |
Subject: |
Re: association list bug? -- version 1.6.4 |
Date: |
Wed, 16 Nov 2005 08:41:11 +1100 |
User-agent: |
Gnus/5.110004 (No Gnus v0.4) Emacs/21.4 (gnu/linux) |
Jon Wilson <address@hidden> writes:
>
> which seems to suggest (incorrectly, obviously) that the arguments to
> both assoc and assoc-ref should be the same. Perhaps, given that it
> seems that a fairly large number of people have misread the manual and
> gotten confused about this, it would be helpful to add a phrase
> explicitly pointing out that the argument order is reversed.
I'll change the section to something like below. Both shorter and
clearer I think.
5.6.11.3 Retrieving Alist Entries
.................................
`assq', `assv' and `assoc' find the entry in an alist for a given key,
and return the `(KEY . VALUE)' pair. `assq-ref', `assv-ref' and
`assoc-ref' do a similar lookup, but return just the VALUE.
-- Scheme Procedure: assq key alist
-- Scheme Procedure: assv key alist
-- Scheme Procedure: assoc key alist
-- C Function: scm_assq (key, alist)
-- C Function: scm_assv (key, alist)
-- C Function: scm_assoc (key, alist)
Return the first entry in ALIST with the given KEY. The return is
the pair `(KEY . VALUE)' from ALIST. If there's no matching entry
the return is `#f'.
`assq' compares keys with `eq?', `assv' uses `eqv?' and `assoc'
uses `equal?'.
-- Scheme Procedure: assq-ref alist key
-- Scheme Procedure: assv-ref alist key
-- Scheme Procedure: assoc-ref alist key
-- C Function: scm_assq_ref (alist, key)
-- C Function: scm_assv_ref (alist, key)
-- C Function: scm_assoc_ref (alist, key)
Return the value from the first entry in ALIST with the given KEY,
or `#f' if there's no such entry.
`assq-ref' compares keys with `eq?', `assv-ref' uses `eqv?' and
`assoc-ref' uses `equal?'.
Notice these functions have the KEY argument last, like other
`-ref' functions, but this is opposite to what what `assq' etc
above use.
When the return is `#f' it can be either KEY not found, or an
entry which happens to have value `#f' in the `cdr'. Use `assq'
etc above if you need to differentiate these cases.