From: Zelphir Kaltstahl <zelphirkaltstahl@posteo.de>
To: guile-user@gnu.org
Subject: Re: Surprising behavior of eq?
Date: Sun, 20 Sep 2020 15:09:30 +0200 [thread overview]
Message-ID: <bae0d6aa-b0fb-e835-5a01-03fb34c46650@posteo.de> (raw)
In-Reply-To: <8e1d9874-4659-cca5-03da-c2c0df102c56@posteo.de>
And I've noticed something more about equality stuff in the context of
tests:
~~~~
(eqv? "a" "a")
$3 = #t
;; but
(define char->string
(λ (c)
(list->string
(list c))))
(import
;; unit tests
(srfi srfi-64))
(test-begin "string-utils-test")
(test-group
"char-to-string-test"
(test-eqv "char->string converts a character to a string"
"a"
(char->string #\a)))
(test-end "string-utils-test")
%%%% Starting test string-utils-test (Writing full log to "string-utils-test.log")
$2 = ("string-utils-test")
:19: FAIL char->string converts a character to a string
# of unexpected failures 1
~~~~
So while (eqv? ...) gives the correct (?) result, the test procedure
(test-eqv ...) which seems to indicate using (eqv? ...) via its name
does not think of the two strings as equivalent.
On 20.09.20 14:19, Zelphir Kaltstahl wrote:
> Sorry, I misclicked "send" when I wanted to further edit my e-mail ...
>
> My Guile version is:
>
> ~~~~
> (version)
> $6 = "3.0.4"
> ~~~~
>
> On 20.09.20 14:16, Zelphir Kaltstahl wrote:
>> Hello Guile users,
>>
>> I just noticed something weird about eq?.
>>
>> My Guile version is:
>>
>>
>> I get the different results, depending on whether I define some
>> bindings in a let or using define:
>>
>> (In Emacs Geiser:)
>>
>> ~~~~
>> (define x '(10 9))
>> (define y '(10 9))
>> (eq? x y)
>> $2 = #f
>>
>> (let ([x '(10 9)]
>> [y '(10 9)])
>> (eq? x y))
>> $3 = #t
>> ~~~~
>>
>> Is this intentional or a bug?
>>
>> I first noticed something strange when writing the following code:
>>
>> ~~~~DEFINITION~~~~
>> (define make-multiple-list-remover
>> (λ (equal-proc)
>> (λ (lst unwanted)
>> (let loop ([remaining-list lst])
>> (cond
>> [(null? remaining-list)
>> '()]
>> [(equal-proc (car remaining-list) unwanted)
>> (loop (cdr remaining-list))]
>> [else
>> (cons (car remaining-list)
>> (loop (cdr remaining-list)))])))))
>> ~~~~
>>
>> ~~~~TEST~~~~
>> (let ([a '(9 10)]
>> [b '(9 10)])
>> (test-equal "make-multiple-list-remover-03"
>> `(1 2 (3) (4) ,a)
>> ((make-multiple-list-remover eq?)
>> `(a b (c) (d) ,a) b)))
>> ~~~~
>>
>> I was wondering, why the test fails. I think (eq? ...) should not be
>> able to see the equivalence of both lists a and b, just like when
>> defined using (define ...).
>>
>> I can also run it in the REPL and see the difference:
>>
>> ~~~~
>> (define a '(9 10))
>> (define b '(9 10))
>> ((make-multiple-list-remover eq?)
>> `(a b (c) (d) ,a) b)
>> $4 = (a b (c) (d) (9 10))
>>
>> (let ([a '(9 10)]
>> [b '(9 10)])
>> ((make-multiple-list-remover eq?)
>> `(a b (c) (d) ,a) b))
>> $5 = (a b (c) (d))
>> ~~~~
>>
>> Somehow the bindings of let seem to be different from the bindings
>> created using define. What about using define inside let?
>>
>> ~~~~
>>
>> ~~~~
>> --
>> repositories: https://notabug.org/ZelphirKaltstahl
> Somehow the bindings of let seem to be different from the bindings
> created using define. What about using define inside let?
>
> ~~~~
> (let ([unrelated 'bla])
> (define a '(9 10))
> (define b '(9 10))
> ((make-multiple-list-remover eq?)
> `(a b (c) (d) ,a) b))
> $7 = (a b (c) (d))
> ~~~~
>
> So there the define usage also differs from when I use define on the top
> level. Perhaps that is the difference? On which level the bindings are
> defined?
>
> Regards,
> Zelphir
>
--
repositories: https://notabug.org/ZelphirKaltstahl
next prev parent reply other threads:[~2020-09-20 13:09 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-20 12:16 Surprising behavior of eq? Zelphir Kaltstahl
2020-09-20 12:19 ` Zelphir Kaltstahl
2020-09-20 12:58 ` Christopher Lemmer Webber
2020-09-20 13:09 ` Zelphir Kaltstahl [this message]
2020-09-20 13:52 ` John Cowan
2020-09-20 15:37 ` Zelphir Kaltstahl
2020-09-20 16:18 ` tomas
2020-09-20 17:05 ` John Cowan
2020-09-20 20:51 ` Linus Björnstam
2020-09-20 21:42 ` John Cowan
2020-09-20 13:57 ` Stefan Schmiedl
2020-09-20 15:42 ` Zelphir Kaltstahl
2020-09-20 17:26 ` Taylan Kammer
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