clisp-devel

(format ... "~A" (apply #'format nil errorstring arguments))

[Sam S. <sd...@gn...>]

Bruno,

In clos-method2.lisp and many other places you have this pattern:

--8<---------------cut here---------------start------------->8---
(defmacro program-error-reporter (caller)
  `#'(lambda (form detail errorstring &rest arguments)
       (apply #'sys::lambda-list-error form detail
              "~S: ~A" ,caller (apply #'format nil errorstring arguments))))
--8<---------------cut here---------------end--------------->8---

Why not

--8<---------------cut here---------------start------------->8---
(defmacro program-error-reporter (caller)
  `#'(lambda (form detail errorstring &rest arguments)
       (apply #'sys::lambda-list-error form detail
              "~S: ~?" ,caller errorstring arguments)))
--8<---------------cut here---------------end--------------->8---

The only place where the second pattern is used is invalid-method-error
and method-combination-error in close-methcomb2.

Thanks.

--
Sam Steingold (http://sds.podval.org/) on darwin Ns 10.3.1504
http://steingoldpsychology.com http://www.childpsy.net http://think-israel.org
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You won't get smarter by calling me a fool.

Re: (format ... "~A" (apply #'format nil errorstring arguments))

[Bruno H. <br...@cl...>]

Hi Sam,

> In clos-method2.lisp and many other places you have this pattern:
> 
> --8<---------------cut here---------------start------------->8---
> (defmacro program-error-reporter (caller)
>   `#'(lambda (form detail errorstring &rest arguments)
>        (apply #'sys::lambda-list-error form detail
>               "~S: ~A" ,caller (apply #'format nil errorstring arguments))))
> --8<---------------cut here---------------end--------------->8---
> 
> Why not
> 
> --8<---------------cut here---------------start------------->8---
> (defmacro program-error-reporter (caller)
>   `#'(lambda (form detail errorstring &rest arguments)
>        (apply #'sys::lambda-list-error form detail
>               "~S: ~?" ,caller errorstring arguments)))
> --8<---------------cut here---------------end--------------->8---

Both are equivalent. I find the first one easier to understand,
because ~S, ~A, and APPLY are very familiar to everyone, whereas I wouldn't
remember how ~? works exactly - there are two cases - without looking up
CLHS 22.3.7.6.

The other possible explanation is that FORMATTER of ~? was not completely
implemented when I wrote clos-method2.lisp, and I dared to use ~? only after
it was efficient enough.

Bruno

Re: (format ... "~A" (apply #'format nil errorstring arguments))

[Bruno H. <br...@cl...>]

Sam wrote on 2017-08-02:
> In clos-method2.lisp and many other places you have this pattern:
> 
> --8<---------------cut here---------------start------------->8---
> (defmacro program-error-reporter (caller)
>   `#'(lambda (form detail errorstring &rest arguments)
>        (apply #'sys::lambda-list-error form detail
>               "~S: ~A" ,caller (apply #'format nil errorstring arguments))))
> --8<---------------cut here---------------end--------------->8---
> 
> Why not
> 
> --8<---------------cut here---------------start------------->8---
> (defmacro program-error-reporter (caller)
>   `#'(lambda (form detail errorstring &rest arguments)
>        (apply #'sys::lambda-list-error form detail
>               "~S: ~?" ,caller errorstring arguments)))
> --8<---------------cut here---------------end--------------->8---
> 
> The only place where the second pattern is used is invalid-method-error
> and method-combination-error in close-methcomb2.

I replied:
> Both are equivalent.

Not always. When the format string contains directives that are sensitive
on the current column position (tabulate, justification, all pretty-printing
directives) or newline state (fresh-line, elastic-newline), the two idioms
may produce different results.

I don't know whether this has an impact on your change from 2017-08-02.

Bruno

Re: (format ... "~A" (apply #'format nil errorstring arguments))

[Sam S. <sd...@gn...>]

> * Bruno Haible <oe...@py...t> [2017-08-23 22:09:17 +0200]:
>
> Sam wrote on 2017-08-02:
>> In clos-method2.lisp and many other places you have this pattern:
>> 
>> --8<---------------cut here---------------start------------->8---
>> (defmacro program-error-reporter (caller)
>>   `#'(lambda (form detail errorstring &rest arguments)
>>        (apply #'sys::lambda-list-error form detail
>>               "~S: ~A" ,caller (apply #'format nil errorstring arguments))))
>> --8<---------------cut here---------------end--------------->8---
>> 
>> Why not
>> 
>> --8<---------------cut here---------------start------------->8---
>> (defmacro program-error-reporter (caller)
>>   `#'(lambda (form detail errorstring &rest arguments)
>>        (apply #'sys::lambda-list-error form detail
>>               "~S: ~?" ,caller errorstring arguments)))
>> --8<---------------cut here---------------end--------------->8---
>> 
>> The only place where the second pattern is used is invalid-method-error
>> and method-combination-error in close-methcomb2.
>
> I replied:
>> Both are equivalent.
>
> Not always. When the format string contains directives that are
> sensitive on the current column position (tabulate, justification, all
> pretty-printing directives) or newline state (fresh-line,
> elastic-newline), the two idioms may produce different results.

Valid point, and, I think, an excellent argument in favor of the second
version.

Thanks

-- 
Sam Steingold (http://sds.podval.org/) on darwin Ns 10.3.1504
http://steingoldpsychology.com http://www.childpsy.net
http://honestreporting.com http://mideasttruth.com
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