Compositional Programming (Artifact)

Our main paper presents CP, a Compositional Programming language in a statically typed modular programming style. This artifact includes its Haskell implementation, together with several examples and three case studies written in CP. All code snippets in our main paper can be type-checked and run using our CP interpreter

Direct Foundations for Compositional Programming (Artifact)

Our companion paper proposes a new formulation of the ?_{i}^{+} calculus with disjoint polymorphism and a merge operator based on Type-Directed Operational Semantics. The artifact contains Coq formalization of the ?_{i}^{+} calculus and our new implementation of the CP language, which demonstrates the new ?_{i}^{+} can serve as the direct foundation for Compositional Programming

Direct Foundations for Compositional Programming

The recently proposed CP language adopts Compositional Programming: a new modular programming style that solves challenging problems such as the Expression Problem. CP is implemented on top of a polymorphic core language with disjoint intersection types called ?_{i}^{+}. The semantics of ?_{i}^{+} employs an elaboration to a target language and relies on a sophisticated proof technique to prove the coherence of the elaboration. Unfortunately, the proof technique is technically challenging and hard to scale to many common features, including recursion or impredicative polymorphism. Thus, the original formulation of ?_{i}^{+} does not support the two later features, which creates a gap between theory and practice, since CP fundamentally relies on them. This paper presents a new formulation of ?_{i}^{+} based on a type-directed operational semantics (TDOS). The TDOS approach was recently proposed to model the semantics of languages with disjoint intersection types (but without polymorphism). Our work shows that the TDOS approach can be extended to languages with disjoint polymorphism and model the full ?_{i}^{+} calculus. Unlike the elaboration semantics, which gives the semantics to ?_{i}^{+} indirectly via a target language, the TDOS approach gives a semantics to ?_{i}^{+} directly. With a TDOS, there is no need for a coherence proof. Instead, we can simply prove that the semantics is deterministic. The proof of determinism only uses simple reasoning techniques, such as straightforward induction, and is able to handle problematic features such as recursion and impredicative polymorphism. This removes the gap between theory and practice and validates the original proofs of correctness for CP. We formalized the TDOS variant of the ?_{i}^{+} calculus and all its proofs in the Coq proof assistant

Natural Fiber-Anchored Few-Layer Graphene Oxide Nanosheets for Ultrastrong Interfaces in Poly(lactic acid)

The development of high-performance graphene oxide (GO) nanocomposites is challenged by the lack of a feasible and effective route to disperse and exfoliate GO nanosheets, as well as technical gaps in providing precision control over the interfacial interactions. Here we disclose an all-aqueous processing method to immobilize few-layer extended GO nanosheets at ramie fiber driven by hydrogen bonding. The reinforcing efficacy of GO-functionalized ramie (GOFR) was examined in a poly­(lactic acid) (PLA) matrix, wherein the GOFR provided large active surfaces to induce chain ordering and lamellar organization. It permitted the preferable formation of well-organized PLA transcrystallinity at GOFR, in contrast to calabash-like and less-ordered transcrystallinity induced by pristine ramie due to the inferior nucleation activity. The transcrystallization kinetics and lamellar orientation degree were significantly facilitated by the addition of chain mobility accelerator in PLA, permitting the formation of prevailing transcrystallinity with large sizes at GOFR. The profound control of interphase morphology conferred remarkable improvements in interfacial properties with weak relation to crystallization temperature, as indicated by an over 3-fold increase in interfacial shear strength between GOFR and PLA matrix compared to the counterparts incorporated with pristine ramie. The effort reveals the appealing application of natural fibers as an ideal template to extend GO nanosheets, potentially motivating further efforts toward revolutionary advancements occurring in many fields of materials science and nanotechnology