arXiv subjects

Tsung-Ju Chiang

Publications and source records attributed to Tsung-Ju Chiang.

2 recordsLinked to original sources

arXiv2021

Longest segment of balanced parentheses -- an exercise in program inversion in a segment problem (Functional Pearl)

Given a string of parentheses, the task is to find the longest consecutive segment that is balanced, in linear time. We find this problem interesting because it involves a combination of techniques: the usual approach for solving segment problems, and a theorem for constructing the inverse of a function -- through which we derive an instance of shift-reduce parsing.

cs.PL↗

arXiv2021

Deriving monadic quicksort (Declarative Pearl)

To demonstrate derivation of monadic programs, we present a specification of sorting using the non-determinism monad, and derive pure quicksort on lists and state-monadic quicksort on arrays. In the derivation one may switch between point-free and pointwise styles, and deploy techniques familiar to functional programmers such as pattern matching and induction on structures or on sizes. Derivation of stateful programs resembles reasoning backwards from the postcondition.

cs.PL↗