In general, we shall see that recursion is a very powerful technique for dealing
with hierarchical, treelike objects.
2008-01-03
1.The general form of a procedure definition is
(define (<name> <formal parameters>) <body>)
2.The general form of a conditional expression is
Structure and Interpretation of Computer Programs
(cond (<p1> <e1>)
(<p2> <e2>)
(<pn> <en>))
3.The general form of an if expression is
(if <predicate> <consequent> <alternative>)
4.(and <e1> ... <en>)
The interpreter evaluates the expressions <e> one at a time, in left-to-right order. If any <e>
evaluates to false, the value of the and expression is false, and the rest of the <e>'s are not
evaluated. If all <e>'s evaluate to true values, the value of the and expression is the value of the
last one.
l
(or <e1> ... <en>)
The interpreter evaluates the expressions <e> one at a time, in left-to-right order. If any <e>
evaluates to a true value, that value is returned as the value of the or expression, and the rest of
the <e>'s are not evaluated. If all <e>'s evaluate to false, the value of the or expression is false.
l
(not <e>)
The value of a not expression is true when the expression <e> evaluates to false, and false
otherwise.
