What is wrong with this answer-CodePudding

(define inc (lambda(x)((  x 1 ))))

I created the line of code above as an answer to the question

"Create a function called "inc" which will be given a numeric argument, and returns a number larger by one. For instance, (inc 6) => 7"

CodePudding user response：

You have an extra set of parentheses. You want

(define inc (lambda(x)(  x 1 )))

instead of

(define inc (lambda(x)((  x 1 ))))

CodePudding user response：

Probably the most common Scheme & Lisp problem is having too many parentheses.

The correct syntax is (lambda (parameters) expression), not (lambda (parameters) (expression)).
(That is, you should not wrap the function body in parentheses.)

In your case, you have

(inc 6)

which is

((lambda(x)((  x 1 ))) 6)

which is

((  6 1))

which is

(7)

which is not the same as 7, but an attempt to call 7 as a parameterless procedure.

You should write

(define inc (lambda (x) (  x 1)))

(define (inc x) (  x 1))