This paper studies a parsing method for strings containing placeholders, each of which may be later replaced by a string derived from the corresponding nonterminal symbol. Such a method potentially applies to parallel/distributed parsing, parsing for templates, modular syntax definitions, and so on. This paper investigates whether the introduction of the placeholder preserves the class of the grammar and proves the following two facts. First, the class of LR( k )grammars is preserved if k ≥ 1 and every nonterminal derives at least one nonempty string; hence, we can apply the standard LR parsing algorithm for parsing strings with placeholders. Second, the class of LR(0) is not. These results extend the preceding study for the LL(1) grammars.

Fine-grained logs of programmers’ activities serve as research material in various fields of computer science. For activities in a traditional environment, there is a publicly available dataset. However, to our knowledge, no comparable dataset exists for activities in a cell-based computational notebook environment. This paper presents an open dataset of activities in the Jupyter Notebook. The dataset comprises the activity logs of 21 programmers who worked on a one-hour data science task in our log collection experiment. The dataset would contribute to understanding programmers’ workflows in cell-based notebook environments and evaluating proposals for those environments.

While some promote method chaining as a good practice for improving code readability, others refer to it as a bad practice that worsens code quality. In this paper, we first investigate whether method chaining is a programming style accepted by real-world programmers. To answer this question, we collected 2,814 Java repositories on GitHub and analyzed historical trends in the frequency of method chaining. The results of our analysis revealed the increasing use of method chaining; 23.1% of method invocations were part of method chains in 2018, whereas only 16.0% were such invocations in 2010. We then explore language features that are helpful to the method-chaining style but have not been supported yet in Java. For this aim, we conducted manual inspections of method chains that are randomly sampled from the collected repositories. We also estimated how effective they are to encourage the method-chaining style if they are adopted in Java.