Question

I’m new to scheme. When I run the following code

(define lst '(1))

(let ((func1 (lambda lst 
               (begin (display lst)
                      lst))))
  (begin (display lst) 
         (func1 lst)))

I got (1)((1))'((1)), which means lst displays as (1) when called in the fourth line, but when send it to the function func1, it becomes ((1)). What exactly happened here?

Answer 1

(lambda Args E) means: bind the variable-length argument list of this function to Args. E.g.

(define f (lambda args `(got ,(length args) arguments)))
(display (f 'foo 'bar 'baz))

will print (got 3 arguments). If you change the lambda expression to

(lambda (lst) (begin (display lst) lst))
;;;     ^---^

then the function will print, and return, its single argument.