You can take the minimum of two SDFs, which more or less gives you an SDF for their union. The maximum is the intersection. A few years ago I wrote a DSL that w

You can take the minimum of two SDFs, which more or less gives you an SDF for their union. The maximum is the intersection. A few years ago I wrote a DSL that writes the SDFs for you, for my university programming languages course. https://github.com/SebastianMestre/school/tree/master/university/sdf-dsl https://github.com/SebastianMestre/school/tree/master/univer...