A key idea of this language is that you _don't_ give up control over your data structures. You program your algorithm against abstract data structures, as in mo

A key idea of this language is that you _don't_ give up control over your data structures. You program your algorithm against abstract data structures, as in most high-performance DSLs, but then you _explicitly control_ the implementation of those abstract data structures as physical hierarchical structures. (You can get a taste for this in the `layout` block in Fig. 1.)