Note that you can use symbols with the case construct. In other words, these
two expressions are equivalent if str is a string:
(cond ((string=? str "foo") 111)
((string=? str "bar") 222)
(else 333))
and
(case (string->symbol str)
((foo) 111)
((bar) 222)
(else 333))
Marc
> On Jan 19, 2017, at 5:32 AM, Damien MATTEI <[email protected]> wrote:
>
> Hello Manuel,
> i forward my answer because it seems impossible to reach both bigloo and kawa
> mailing list ,messages do not go in kawa,only bigloo mailing list.
>
> i know R5RS specify to use eq? predicate for comparison but this exclude the
> use of strings in programming with CASE
> of course i could use COND or try to write a macro as i'm doing.
> Damien
> ---------- Message transmis ----------
>
> Sujet : Re: behavior of CASE with strings PART 2
> Date : jeudi 19 janvier 2017
> De : Damien MATTEI <[email protected]>
> À : [email protected]
>
> Le Thursday 19 January 2017 05:53:05 Per Bothner, vous avez écrit :
>>
>> On 01/17/2017 10:36 PM, Per Bothner wrote:
>>> I think this is something to think of for the Kawa 3.0 release,
>>> using the new PATTERN construct in each clause.
>>
>> The invoke branch has a 'match' form, which has the syntax:
>>
>> (match TARGET-EXPR (PATTERN BODY...) ...)
>>
>> This matches TARGET-EXPR against each PATTERN, until one matches,
>> at which point the BODY... forms are evaluated.
>>
>> This is the 'match' form from Racket:
>> https://docs.racket-lang.org/guide/match.html
>> https://docs.racket-lang.org/reference/match.html
>>
>> Unfortunately, the implemented forms of PATTERN are very
>> limited, but the intention to allow literals and quoted forms.
>> These will be compared using equal?, so you will be able to write:
>>
>> (match "yes"
>> ("no" #f)
>> ("yes" #t))
>>
>> THIS IS NOT YET IMPLEMENTED. (It's not conceptually hard; I just need to
>> decide the best way to present such match forms.)
>>
>> I think this is the generalization of 'case' that we're looking for.
>
> Hi Per,
>
> thanks for your answer...
> i read the many answers to the mailing list about CASE and STRINGS and
> delayed my answer because i
> wanted to answer after having a solution (still not done)
>
> i understand the various implementation of Scheme follow or not the R5RS and
> R7RS
> but this could be changed in a future revision because it is limitating to be
> able to use CASE with STRINGS
> in language such as ASP, Java and not Scheme, with Racket it seems that
> equal? predicate is used,
> so probably my code will work with Racket.
>
> i think of many solutions and finalyy begin to write a recursive macro
> implementing a case-string
> but i'm facing proble with multiple "ellipsis" in a recursive macro and
> wanted to debug it this morning
> when i read your last message, so here it is:
>
> ;; CASE adapted for string comparison
>
> (define-syntax case-string
>
> (syntax-rules ()
>
> ((_ var
> (lst res)
> (... ...)
> (else => res-else))
>
> (if (member var lst)
> res
> (case var
> (... ...)
> (else => res-else))))
>
> ((_ var
> (else => res-else))
>
> res-else)))
>
> ellispsis have to be fixed and the behavior seems to be not defined in R5RS i
> tried many scheme and it behave diffrently, even in Racket with #lang R5RS
> it does not work now
>
> Damien
>
> --
> [email protected], [email protected], UNS / OCA / CNRS
>
> -------------------------------------------------------
>
> --
> [email protected], [email protected], UNS / OCA / CNRS
