[Haskell-beginners] map increases length of list

[Alan Mock]

That's because [0,60,..359] is not the same as [0,60..359] ::  
[Double].  So what you're passing to degreesToRadians is  
[0.0,60.0,120.0,180.0,240.0,300.0,360.0] and not  
[0,60,120,180,240,300].  I don't know why the Double version adds  
another number, though.

On Jun 17, 2009, at 4:35 PM, Aaron MacDonald wrote:

> For some reason, the map function returns a list that has one more  
> element than my input list.
>
> My input list is a range defined by [0, 60..359] (should translate  
> into [0,60,120,180,240,300]).
>
> The function I'm giving to map is defined this way:
> -----
> degreesToRadians :: Double -> Double
> degreesToRadians degrees = degrees * (pi / 180)
> -----
>
> This is how I'm calling map overall:
> -----
> > map degreesToRadians [0,60..359]
> [0.0,1.0471975511965976,2.0943951023931953,3.141592653589793,4.1887902047863905,5.235987755982989,6.283185307179586 
> ]
> -----
>
> As you can hopefully see, there are seven elements instead of six.  
> Getting the length confirms this:
> -----
> > length [0,60..359]
> 6
> > length $ map degreesToRadians [0,60..359]
> 7
> -----
>
> I do not seem to get this behaviour with the length if I either  
> substitute the degreesToRadians function or substitute the  
> [0,60..359] range.
>
> P.S. Is there a built-in function to convert degrees to radians and  
> vice-versa?
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