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From: Manuel.Serrano@inria.fr
To: Damien MATTEI <Damien.Mattei@unice.fr>
Cc: Kawa mailing list <kawa@sourceware.org>, bigloo@sophia.inria.fr
Subject: Re: [bigloo] behavior of CASE with strings
Date: Mon, 16 Jan 2017 13:34:00 -0000
Message-ID: <2017116143211.587ccb5b@redrock.inria.fr>
References: <201701121129.54147.Damien.Mattei@unice.fr>
Reply-To: Manuel.Serrano@inria.fr
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Hi Damien,

Bigloo complies with the R5RS specification (see section 4.2) that says:

-----|-----|-----|-----|-----|-----|-----|-----|-----|-----|-----|-----|-----
case <key> <clause1> <clause2> ...,	library syntax
Syntax: <Key> may be any expression. Each <clause> should have the form

((<datum1> ...,) <expression1> <expression2> ...,),

where each <datum> is an external representation of some object. All the <datum>s must be distinct. The last <clause> may be an ``else clause,'' which has the form

(else <expression1> <expression2> ...,).

Semantics: A case expression is evaluated as follows. <Key> is evaluated and its result is compared against each <datum>. If the result of evaluating <key> is equivalent (in the sense of eqv?; see section Equivalence predicates) to a <datum>, then the expressions in the corresponding <clause> are evaluated from left to right and the result(s) of the last expression in the <clause> is(are) returned as the result(s) of the case expression. If the result of evaluating <key> is different from every <datum>, then if there is an else clause its expressions are evaluated and the result(s) of the last is(are) the result(s) of the case expression; otherwise the result of the case expression is unspecified.

(case (* 2 3)
  ((2 3 5 7) 'prime)
  ((1 4 6 8 9) 'composite))            =>  composite
(case (car '(c d))
  ((a) 'a)
  ((b) 'b))                            =>  unspecified
(case (car '(c d))
  ((a e i o u) 'vowel)
  ((w y) 'semivowel)
  (else 'consonant))                   =>  consonant
-----|-----|-----|-----|-----|-----|-----|-----|-----|-----|-----|-----|-----

You can observe that with:

(pp (expand '(case x (("foo") 1) (("bar" ) 2))))
=>
(let ((case-value x))
  (if (eqv? case-value '"foo")
    1
    (if (eqv? case-value '"bar") 2 #unspecified)))

Cheers,

-- 
Manuel