lisp error : "should be a lambda expression"

Question

i am new to lisp and in my code i want to convert 3 first bit to integer and check if number of ones in next bits is equal to that or not this is my code:

 (defun new (vi n res)(
(cond ( (= vi nil) ((cond ((= 0 res) t) )))
 (    (= 2 n) (new (cdr vi) 1 (* (car vi) 4)) ) 
      ((= 1 n) (new (cdr vi) 0 (+ (res) (* (car vi) 2)) ))  
      ((= 0 n) (new (cdr vi) -1 (+ (res) (car vi ))  ))
       ((= vi nil) (nil))
      ((= -1 n) (new (cdr vi) -1 (- res (car vi)) )) )))

but it has this error: (COND ((= VI NIL) ((COND ((= 0 RES) T)))) ((= 2 N) (NEW (CDR VI) 1 (* (CAR VI) 4))) ((= 1 N) (NEW (CDR VI) 0 (+ (RES) (* (CAR VI) 2)))) ((= 0 N) (NEW (CDR VI) -1 (+ (RES) (CAR VI)))) ((= VI NIL) (NIL)) ((= -1 N) (NEW (CDR VI) -1 (- RES (CAR VI))))) should be a lambda expression

delta · Accepted Answer · 2020-07-10 06:06:16Z

1

You put extra () around for cond, which makes lisp think it should be callable, remove extra () would fix the issue.

 (defun new (vi n res)
    (cond ((= vi nil) (cond ((= 0 res) t) ))
          ((= 2 n) (new (cdr vi) 1 (* (car vi) 4))) 
          ((= 1 n) (new (cdr vi) 0 (+ (res) (* (car vi) 2))))  
          ((= 0 n) (new (cdr vi) -1 (+ (res) (car vi ))))
          ((= vi nil) (nil))
          ((= -1 n) (new (cdr vi) -1 (- res (car vi))))))

answered Jul 10, 2020 at 6:06

delta

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5 Comments

Mohammadali Eftekhari Over a year ago

this problem solved but when I give parameters to it like this :(new ( 0 1 0 0 0 0 1 0 0 1 0) 2 0 ) it errors: - EVAL: 0 is not a function name; try using a symbol instead

Rainer Joswig Over a year ago

@MohammadaliEftekhari: 0 is not a function, so the error is correct.

Mohammadali Eftekhari Over a year ago

how can i fix this i dont want 0 to be a function?

Rainer Joswig Over a year ago

@MohammadaliEftekhari there is a function LIST to create a list. There are some basic tutorials about Lisp you might need to check out first.

Mohammadali Eftekhari Over a year ago

i read some but this language is a little hard to understand so i wanted to learn with some examples

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