Print Page - The length of nil value

Title: The length of nil value
Post by: iNPRwANG on April 17, 2012, 08:10:04 PM

This is code:

Code Select Expand

(setq mylst '(nil nil nil nil nil nil nil nil nil nil nil nil))
(dolist (item mylst) (println (length item)))

Why the result is:

3

3

3

3

3

3

3

3

3

3

3

3

3

3

3

3

3

3

3

3

3

3

3

3

Title: Re: The length of nil value
Post by: rickyboy on April 17, 2012, 08:35:44 PM

Because (length 'nil) is 3.

On the other hand, (length nil) is 0.

Title: Re: The length of nil value
Post by: Lutz on April 17, 2012, 08:45:47 PM

Length applied to a symbol returns the length of the symbol name:

http://www.newlisp.org/downloads/newlisp_manual.html#length

Title: Re: The length of nil value
Post by: iNPRwANG on April 17, 2012, 09:37:35 PM

OK, thx.

The difference with common lisp is: In common lisp the (length 'nil) is zero, and in newlisp is the symbols length.

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