Add Num instance for Behavior about reactive-banana HOT 8 CLOSED

Can we open some more dialog on this? I don't really buy the only comment against this - if you try and use operators that aren't part of Num, you get a type error as expected. That's mildly annoying, but not a disaster. The Num operators remove a significant amount of noise, especially in game related programming.

from reactive-banana.

I'm in favor now. See #174

from reactive-banana.

Personally, I think this is a bad idea; see this comment.

from reactive-banana.

I think that a Num instance is very useful for animations or audio, but I don't have enough experience with animations to know how useful exactly. For instance, current graphics libraries tend to use vector space operations, like vecAdd and vecSub, so a Num instance wouldn't work.

I would like to leave this open for now. If you have any examples that showcase how life is made simpler with class instances, please let me know!

from reactive-banana.

Has there been any more thought on this? The examples in the original fran tutorial are in my opinion remarkably expressive due to the Num instance.

accelBecky u = moveXY x 0 becky 
   where
     x = -1 + atRate v u
     v =  0 + atRate 1 u

flows u = trailWords motion 
             "Time flows like a river"
   where
     motion = 0.7 *^ vector2XY (cos time)
                               (sin (2 * time))

from reactive-banana.

I'm still undecided.

The operator (*^) is not a member of the Num class, though, right?

from reactive-banana.

That's right - it's part of a vector-space. I guess Conal must have made a VectorSpace instance for Behavior as well.

from reactive-banana.

I realise I never voiced my opinion here. I'd like to mention that I am quite strongly 👍 on Num, Fractional and Floating instances. I would even go further and add IsString a => IsString (Behavior a), but in the work I'm doing this particular case can be hidden behind a newtype. (The numeric stuff however I do want to be working with Behavior and not another type)

from reactive-banana.