Add with alternating signs

[rickyboy]

Among the Code Snippets, "Add with alternating signs" can be improved by replacing the principal procedure, given currently by the following macro definition:

Code: Select all

(define-macro (+-)
  (let (signs (cons 1 (series 1 -1 (- (length (args)) 1))))
    (apply 'add (map 'mul (map eval (args)) signs))))

by a function which does the same thing:

Code: Select all

(define (+-)
  (let (signs (cons 1 (series 1 -1 (- (length (args)) 1))))
    (apply add (map mul signs (args)))))

In addition to shortening the punchline, the function version will execute faster. Please let me know if I missed anything. Thanks! --Rick

[Lutz]

Thanks Rick, I updated: http://newlisp.org/index.cgi?Tips_and_Tricks

Lutz