Fundamentals of CS I (CS151 2001S) : Reference

and - combine (Boolean) results

Basic Version: Booleans

Procedureand
Parametersb1 ... bn, n Boolean values
PurposeDetermines if all the values are true.
ProducesA truth value: true (#t) if all the values are true; false (#f) if any is false.
PreconditionsAll the parameters are Boolean values (unverified).
Examples
> (and #t #t #t)
#t
> (and (< 1 2) (< 2 3))
#t
> (and (odd? 1) (odd? 3) (odd? 5) (odd? 6))
#f
> (and)
#t

Advanced Version: Control

Procedureand
Parametersexp1 ... expn, n expressions
PurposeEvaluates expressions one-by-one until it reaches the end or false.
ProducesThe value of one of the expressions. Returns false (#f) if any of the expressions evaluates to false. Returns the value of the last expression if all the expressions evaluate to something other than false.
Preconditions(None)
PostconditionsEvalutes each of the expressions up to (and including) the first one that returns false. If all of the expressions return a non-false value, evaluates all of the expressions.
Examples
> (and "hello" "goodbye")
"goodbye"
> (and (display "Blah") (newline) "goodbye")
Blah
"goodbye"
> (and (display "Blah") #f (display "Blech"))
Blah
#f

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The source was last modified Wed Jan 31 22:29:25 2001.