CODEWITHSUNDEEP
scheme
cremo97
cremo97

Reputation: 3

let: bad syntax (missing binding pairs or body)

I would like to declare three lists on which to do operations, but using define their value does not change. So I thought I'd use let but it gives me an error.

(let ((A '0)
      (B '0)
      (C '0)
      )
  )

I expect 3 lists but it gives me this error:

let: bad syntax (missing binding pairs or body) in: (let ((A (quote 0)) (B (quote 0)) (C (quote 0))))

Upvotes: 0

Views: 4208

Answers (3)

alinsoar
alinsoar

Reputation: 15793

writing let with no body is the same as defining a lambda function with no body.

(let ((A '0)
      (B '0)
      (C '0)
      )
  )

is the same as writing

(lambda(a b c) ) 0 0 0) ;; here it is not allowed to define function with no statement inside

('0 is evaluated to itself).

Upvotes: 1

Sylwester
Sylwester

Reputation: 48745

(let ((a 0) (b 0) (c 0))
  ;; a, b, c lives inside this let block
  (list a b c)) ;; a body of the let that makes a list (0 0 0)

;; a, b, c from the let block no longer exist

The Scheme report expect you to use the binding for something. Thus after you have defined the bindings of the let it is expected that there is at least one expression inside it that does something. The let is just syntax sugar for this:

;; anonymous lambda call
((lambda (a b c)
   (list a b c))  ;; body of the lambda that makes list (0 0 0)
 0 ; a
 0 ; b
 0); c

Now imagine what this is supposed to do:

;; anonymous lambda call
((lambda (a b c)
  ;; no body that does anything 
  )
 0 ; a
 0 ; b
 0); c

Upvotes: 1

river
river

Reputation: 1028

You did it right but there was code missing

(let ((A '0)
      (B '0)
      (C '0)
      )
  you need code here
  )

Upvotes: 0

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