Oh, just to add that

    let b: uint = uint(a)

    # can be written as:
    let b = uint(a)

The type is inferred from the right hand side during assignment. The only reason I wrote this

    let b: uint = a

is because in my example `a` was an `int`, so

    let b = a

Would infer an `int` type for `b`, which compiles fine, and doesn't show the type mismatch I wanted to present.