slab() is broken

To reproduce:

from sdf import *
f = slab()

Output:

  File "example.py", line 3, in <module>
    f = slab()
  File "C:\Users\Brandon\Documents\GitHub\sdf\sdf\d3.py", line 49, in wrapper
    return SDF3(f(*args, **kwargs))
  File "C:\Users\Brandon\Documents\GitHub\sdf\sdf\d3.py", line 133, in slab
    return intersection(*fs, k=k)
  File "C:\Users\Brandon\Documents\GitHub\sdf\sdf\d3.py", line 54, in wrapper
    return SDF3(f(*args, **kwargs))
TypeError: intersection() missing 1 required positional argument: 'a'```

[fogleman]

In fact, maybe it shouldn’t be defined like a primitive at all. And instead be like an “operator” that functions on another SDF:

sphere(1).cut(z0=-0.2, z1=0.2)

[pomeroyb]

There are a couple primitives that act like that (Plane and non-capped Cylinder). I’ve been differentiating them by referring to them as “non-meshable” in the comments: https://github.com/pomeroyb/sdf/blob/main/sdf/d3.py#L119

But hiding the pseudo-primitives behind a function will probably be easier for new users to understand. Something like sphere(1).hole(radius=0.25) for a cylinder and sphere(1).section((1,1,0) for a plane.