Hsiang-Shang Ko

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Dependently typed programmers are encouraged to use inductive families to integrate constraints with data construction. Different constraints are used in different contexts, leading to different versions of datatypes for the same data structure. Modular implementation of common operations for these structurally similar datatypes has been a longstanding(More)
Relational program derivation is the technique of stepwise refining a relational specification to a program by algebraic rules. The program thus obtained is correct by construction. Meanwhile, dependent type theory is rich enough to express various correctness properties to be verified by the type checker. We have developed a library, AoPA, to encode(More)
Dependently typed programming is hard, because ideally dependently typed programs should share structure with their correctness proofs, but there are very few guidelines on how one can arrive at such integrated programs. McBride's <i>algebraic ornamentation</i> provides a methodological advancement, by which the programmer can derive a datatype from a(More)
Dependent type theory is rich enough to express that a program satisfies an input/output relational specification, but it could be hard to construct the proof term. On the other hand, squiggolists know very well how to show that one relation is included in another by algebraic reasoning. We demonstrate how to encode functional and relational derivations in(More)
Putback-based bidirectional programming allows the programmer to write only one putback transformation, from which the unique corresponding forward transformation is derived for free. The logic of a putback transformation is more sophisticated than that of a forward transformation and does not always give rise to well-behaved bidirectional programs; this(More)
Language designers usually need to implement parsers and printers. Despite being two related programs, in practice they are designed and implemented separately. This approach has an obvious disadvantage: as a language evolves, both its parser and printer need to be separately revised and kept synchronised. Such tasks are routine but complicated and(More)
Language designers usually need to implement parsers and printers. Despite being two intimately related programs, in practice they are often designed separately, and then need to be revised and kept consistent as the language evolves. It will be more convenient if the parser and printer can be unified and developed in one single program, with their(More)
In work on relational databases, the view-update problem is about how to translate update operations on the view table to corresponding update operations on the source table properly. It is a problem that the translation policies are not unique in many situations. Relational lenses try to solve this problem by providing a list of combinators that let the(More)
Bidirectional transformation (bx) approaches provide a systematic way of specifying, restoring, and maintaining the consistency of related models. The current diversity of bx approaches is certainly beneficial, but it also poses challenges, especially when it comes to comparing the different approaches and corresponding bx tools that implement them.(More)