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Scheme procedures always return a return value, which is the value of the last expression executed in the procedure. The return value can be any valid Scheme value, including a complex data structure or a procedure.
Sometimes the user would like to have multiple Scheme expressions in
a procedure. There are two ways that multiple expressions can be
combined. The first is the
begin procedure, which allows
multiple expressions to be evaluated, and returns the value of
the last expression.
guile> (begin (+ 1 2) (- 5 8) (* 2 2)) 4
The second way to combine multiple expressions is in a
In a let block, a series of bindings are created, and then a sequence
of expressions that can include those bindings is evaluated. The
return value of the let block is the return value of the last
statement in the let block:
guile> (let ((x 2) (y 3) (z 4)) (display (+ x y)) (display (- z 4)) … (+ (* x y) (/ z x))) 508