After reading through the PR below, and some blog posts about generalized indexing in `AbstractArrays`

, I am wondering if the code below is the right way to iterate through the rows of a matrix:

```
"Check if argument is a probability vector."
isprobvec{T}(v::AbstractVector{T}) = all(x->x ≥ 0, v) && sum(v) ≈ one(T)
"Check if argument is a probability (stochastic) matrix."
isprobmat(m::AbstractMatrix) = all(i->isprobvec(view(m, i, :)), indices(m, 1))
```