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1.1.7 Scheme conditionals
if
Scheme has an if
procedure:
(if test-expression true-expression false-expression)
test-expression is an expression that returns a boolean
value. If test-expression returns #t
, the if
procedure returns the value of true-expression, otherwise
it returns the value of false-expression.
guile> (define a 3) guile> (define b 5) guile> (if (> a b) "a is greater than b" "a is not greater than b") "a is not greater than b" |
cond
Another conditional procedure in scheme is cond
:
(cond (test-expression-1 result-expression-sequence-1) (test-expression-2 result-expression-sequence-2) ... (test-expression-n result-expression-sequence-n))
For example:
guile> (define a 6) guile> (define b 8) guile> (cond ((< a b) "a is less than b") ... ((= a b) "a equals b") ... ((> a b) "a is greater than b")) "a is less than b" |
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