case

(case <key> <clause1> <clause2> ...)

Description:

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 6.1) 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.

Arguments:

Returns: boolean

Examples:

(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

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