begin special form is used to evaluate expressions in a
The expressions are evaluated sequentially from left to right, and the value of the last expression is returned. This expression type is used to sequence side effects such as input and output.
(define x 0) (begin (set! x 5) (+ x 1)) ⇒ 6 (begin (display "4 plus 1 equals ") (display (+ 4 1))) -| 4 plus 1 equals 5 ⇒ unspecified
Often the use of
begin is unnecessary, because many special forms
already support sequences of expressions (that is, they have an implicit
begin). Some of these special forms are:
case cond define ;“procedure
define” only do fluid-let lambda let let* letrec named-lambda
The obsolete special form
sequence is identical to
It should not be used in new code.