Added comments for isscalar behavior and testing

src/math/scalar.jl

@@ -5,14 +5,18 @@
 Determines whether the Clifford number `x` is a scalar, meaning that all of its blades of nonzero
 grade are zero.
 """
+# TODO: how to test this fallback method which is not used by any internal types?
 function isscalar(x::AbstractCliffordNumber)
     inds = Iterators.filter(!isequal(scalar_index(x)), BitIndices(x))
     return all(iszero, x[i] for i in inds)
 end
 
+# The first index of these types is the scalar index
 isscalar(x::Union{CliffordNumber,EvenCliffordNumber}) = all(iszero, Tuple(x)[2:end])
+# These types cannot be scalars unless they are zero
 isscalar(x::OddCliffordNumber) = iszero(x)
 isscalar(x::KVector) = iszero(x)
+# These types are definitely scalars
 isscalar(::KVector{0}) = true
 isscalar(::BaseNumber) = true