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R4RS 4.2.1 (cond <clause1> <clause2> ...) ==> object
Syntax: Each <clause> should be of the form
(<test> <expression> ...)
where <test> is any expression. The last <clause> may be an "else
clause," which has the form
(else <expression1> <expression2> ...).
Semantics: A COND expression is evaluated by evaluating the <test>
expressions of successive <clause>s in order until one of them
evaluates to a true value (see section see section 6.1 Booleans).
When a <test> evaluates to a true value, then the remaining
<expression>s in its <clause> are evaluated in order, and the result
of the last <expression> in the <clause> is returned as the result
of the entire COND expression. If the selected <clause> contains
only the <test> and no <expression>s, then the value of the <test>
is returned as the result. If all <test>s evaluate to false values,
and there is no ELSE clause, then the result of the conditional
expression is unspecified; if there is an ELSE clause, then its
<expression>s are evaluated, and the value of the last one is
returned.
(cond ((> 3 2) 'greater)
((< 3 2) 'less)) ==> greater
(cond ((> 3 3) 'greater)
((< 3 3) 'less)
(else 'equal)) ==> equal
Some implementations support an alternative <clause> syntax,
(<test> => <recipient>),
where <recipient> is an expression. If <test> evaluates to a true
value, then <recipient> is evaluated. Its value must be a procedure
of one argument; this procedure is then invoked on the value of the
<test>.
(cond ((assv 'b '((a 1) (b 2))) => cadr)
(else #f)) ==> 2
S9fES does support the alternative clause syntax.
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