3.1 Booleans

Scheme has two distinguished constants to represent boolean values: #t for true and #f for false. Uppercase #T and #F are parsed as the same values, but the lowercase forms are preferred.

The boolean? procedure recognizes the two boolean constants. In the result of a test expression for if, cond, and, or, etc., however, any value other than #f counts as true.

Examples:

> (= 2 (+ 1 1))

#t

> (boolean? #t)

#t

> (boolean? #f)

#t

> (boolean? "no")

#f

> (if "no" 1 0)

1