Print Page - Add with alternating signs

Title: Add with alternating signs
Post by: rickyboy on May 18, 2007, 10:20:55 AM

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 Expand
(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 Expand
(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

Title:
Post by: Lutz on May 18, 2007, 11:12:10 AM

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

Lutz

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Forum => Anything else we might add? => Topic started by: rickyboy on May 18, 2007, 10:20:55 AM