Wasn't it Justace Clutter who wrote:
>I am trying to get render a frame with a wave function built in it.  The 
>function is the specific solution after seperation of variables was done.  
>Anyway all that is irrelelvant.  When I try to render the frame it just 
>sits there and does nothing.  the povray process accums time but does not 
>do anyhing and I have to kill it with a sig 9 to get it to exit.  I use 
>Linux if you have not already guessed.  Any information on this would be 
>wonderfull.
>

A fairly minimal piece of code that exhibits the problem is

// This is the entire scene file
#declare F = function {sum(n, 1, 1, 1*(2/(n*1)))}
#debug str(F(0,0,0),5,5)
// -----------------------------

Any attempt to simplify the expression causes the scene to complete, but
does not always return what I consider the right answer.


Consider these:-

  #declare F = function {sum(n, 1, 1, n)}

evaluates to 1.00000, which I reckon is OK, but

  #declare F = function {sum(n, 1, 1, 1*n)}

evaluates to 2.00000, which I reckon is wrong.


  #declare F = function {sum(n, 3.1234, 4.1234, 1)}   => 2.00000 : OK
  #declare F = function {sum(n, 3.1234, 4.1234, 1*1)} => 5.12340
           which is wrong by an amount equal to the initial value of n.

  #declare F = function {prod(n, 1,2, n)}     =>  2.00000 : OK
  #declare F = function {prod(n, 1,2, 1*n)}   =>  4.00000 : wrong
  #declare F = function {prod(n, 1,2, n/1)}   =>  4.00000 : wrong
  #declare F = function {prod(n, 1,2, (n+0))} =>  4.00000 : wrong

-- 
Mike Williams
Gentleman of Leisure

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