Re: [PATCH] Re: not-so-ancient flags

[Carl D. Sorensen]

On 12/13/08 8:04 AM, "Han-Wen Nienhuys" <address@hidden> wrote:

> On Sat, Dec 13, 2008 at 11:48 AM, Reinhold Kainhofer
> <address@hidden> wrote:
> 
>> - -) What's the best way to convert an angle/length pair of polar coordinates
>>    (angle given in degree) to cartesian coordinates in scheme / guile? I
>>    don't want it as a complex number, but as a pair of reals...
> 
> Well, both are equivalent, so I think using complex numbers is
> actually the quickest.
> 

But complex numbers need angles in radians, not degrees, so you at least
need to do some conversion.

Here's a new version that uses complex numbers.

(define (polar->rectangular polar-pair)
 "Convert @code{polar-pair}, a pair containing (magnitude .
angle-in-degrees)
to (x-length . y-length)"
  (let* ((conversion-constant (/ (atan 1 1) 45))
         (complex (make-polar
                    (car polar-pair)
                    (* conversion-constant (cdr polar-pair)))))
     (cons
       (real-part complex)
       (imag-part complex))))


Carl