Subtyping Union Types

@inproceedings{Vouillon2004SubtypingUT,
  title={Subtyping Union Types},
  author={J{\'e}r{\^o}me Vouillon},
  booktitle={CSL},
  year={2004}
}
Subtyping can be fairly complex for union types, due to interactions with other types, such as function types. Furthermore, these interactions turn out to depend on the calculus considered: for instance, a call-by-value calculus and a call-by-name calculus will have different possible subtyping rules. In order to abstract ourselves away from this dependence, we consider a fairly large class of calculi. This allows us to find a subtyping relation which is both robust (it is sound for all calculi… 
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References

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