From: Zelphir Kaltstahl <zelphirkaltstahl@posteo.de>
To: Guile User <guile-user@gnu.org>
Subject: Re: Exception with multiple irritants
Date: Sun, 8 Jan 2023 13:09:23 +0000 [thread overview]
Message-ID: <eafec672-d00f-9726-0fe4-847d24196193@posteo.de> (raw)
In-Reply-To: <e2a9ffef-4516-2d86-034e-a7374b5a1026@posteo.de>
On 11/25/22 01:03, Zelphir Kaltstahl wrote:
> Hello Guile Users!
>
> I have a question regarding exception creation in general and maybe in
> specific about irritants.
>
> I created a new exception type:
>
> ~~~~
> (library (exceptions)
> (export make-contract-violated-exception-plain
> make-exception-contract-violated-compound
> &contract-violated
> contract-violated-exception?)
> (import (except (rnrs base) let-values)
> (only (guile)
> lambda* λ
> record-constructor
> make-exception-type
> &programming-error)
> (ice-9 exceptions))
>
> ;; Create a custom exception type, to make it clearer,
> ;; that a contract failed, and not only an arbitrary
> ;; assertion.
> (define &contract-violated
> (make-exception-type
> ;; name of the new exception type
> '&contract-violated
> ;; parent exception type
> &programming-error
> ;; list of values the constructor of the exception
> ;; takes and their names in the record
> '()))
>
> (define make-contract-violated-exception-plain
> ;; record-constructor is a procedure, which will return
> ;; the constructor for any record.
> (record-constructor
> ;; Create an exception type, which is a record. This
> ;; record has a constructor, which we can name using
> ;; define for example.
> &contract-violated))
>
> (define contract-violated-exception?
> (exception-predicate &contract-violated))
>
> (define make-exception-contract-violated-compound
> (λ (message origin irritants)
> (make-exception
> (make-contract-violated-exception-plain)
> (make-exception-with-message message)
> (make-exception-with-origin origin)
> (make-exception-with-irritants irritants)))))
> ~~~~
>
> However, I realized, when a contract is violated, it would be nice to not only
> see the violated contract or condition as irritants, but also the values of
> the irritants. So I simply tried adding them as well in the exception:
>
> ~~~~
> ...
> (define make-exception-contract-violated-compound
> (λ (message origin irritants irritant-values)
> (make-exception
> (make-contract-violated-exception-plain)
> (make-exception-with-message message)
> (make-exception-with-origin origin)
> (make-exception-with-irritants irritants)
> (make-exception-with-irritants irritant-values))))
> ...
> ~~~~
>
> Note, that now I have 2 times `make-exception-with-irritants` in there. This
> does not cause an error and `exception-irritants` still returns the first
> irritants, so my tests also all still pass, as I have not tested for there not
> to be other exception attributes.
>
> For example a violated exception example could look like this:
>
> ~~~~
> (define-with-contract bla
> (require (> foo 10))
> (ensure (> <?> 0))
> (λ (foo)
> (- 20 foo)))
>
> (bla 10)
>
> ice-9/boot-9.scm:1685:16: In procedure raise-exception:
> ERROR:
> 1. &contract-violated
> 2. &message: "contract violated"
> 3. &origin: bla
> 4. &irritants: (> foo 10)
> 5. &irritants: (> 10 10)
> ~~~~
>
> Nice! Now I have the value of `foo` in this case as well and that could be
> useful information in cases, when I get a violated contract unexpectedly.
>
> However, having irritants twice seems a bit weird. Is this something, that is
> safe to do? Something expected and probably unchanging in future versions of
> GNU Guile? Or does it merely work by chance?
>
> I could always make another exception type like
> "exception-with-irritant-values" or something and use that, instead of a
> second "with irritants" call.
>
> Best regards,
> Zelphir
Hi!
Does anyone know this? Is it OK and reliable to have more than 1
`exception-with-irritant-values` in a compound exception?
Regards,
Zelphir
--
repositories: https://notabug.org/ZelphirKaltstahl
next prev parent reply other threads:[~2023-01-08 13:09 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-11-25 0:03 Exception with multiple irritants Zelphir Kaltstahl
2023-01-08 13:09 ` Zelphir Kaltstahl [this message]
2023-01-08 17:31 ` Maxime Devos
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