4.2 Booleans

True and false booleans are represented by the values #t and #f, respectively, though operations that depend on a boolean value typically treat anything other than #f as true. The #t value is always eq? to itself, and #f is always eq? to itself.

See Reading Booleans for information on reading booleans and Printing Booleans for information on printing booleans.

See also and, or, andmap, and ormap.

Note that immutable? is not a general predicate for immutability (despite its name). It works only for a handful of datatypes for which a single predicate—string?, vector?, etc.—recognizes both mutable and immutable variants of the datatype. In particular, immutable? produces #f for a pair, even though pairs are immutable, since pair? implies immutability.

See also immutable-string?, mutable-string?, etc.

4.2.1 Boolean Aliases

In the two argument case, returns #t if neither of the arguments is a true value.

Same as (if expr1 expr2 #t).

If exactly one of b1 and b2 is not #f, then return it. Otherwise, returns #f.

4.2.2 Mutability Predicates

Added in version 8.9.0.3 of package base.