Traditionally, in linearly typed languages, consuming a linear resource is synonymous with its syntactic occurrence in the program. However, under the lens of non-strict evaluation, linearity can be further understood semantically, where a syntactic occurrence of a resource does not necessarily entail using that resource when the program is executed. While this distinction has been largely unexplored, it turns out to be inescapable in Haskell’s optimising compiler, which heavily rewrites the source program in ways that break syntactic linearity but preserve the program’s semantics. We introduce Linear Core, a novel system which accepts the lazy semantics of linearity statically and is suitable for lazy languages such as the Core intermediate language of the Glasgow Haskell Compiler. We prove that Linear Core is sound, guaranteeing linear resource usage, and that multiple optimising transformations preserve linearity in Linear Core while failing to do so in Core. We have implemented Linear Core as a compiler plugin to validate the system against linearity-heavy libraries, including linear-base .

Context: The use of Creativity and Design Thinking (C&DT) techniques favor the generation of new ideas based on the needs of users and stakeholders, and can support software developers during the process of requirements elicitation. Objectives: In this work, we aim to identify C&DT techniques to perform requirements elicitation proposed in the literature and in the industry and investigate the perception of software developers about using these techniques. Methods: We conducted a systematic literature review (SLR) to identify the C&DT techniques in the literature and a regional survey with software development teams from several companies in Brazil to identify which techniques found in the literature are currently being used by organizations. The survey also investigated the level of knowledge that software developers have regarding the C&DT techniques, and whether they agree that the use of these techniques can help to achieve a more effective process of requirements elicitation. Results: In the SLR, we identified 86 C&DT techniques that support requirement elicitation activities. In the survey, most developers outlined that C&DT techniques facilitate requirements elicitation and stated that they have more knowledge and usage experience with DT techniques than creativity techniques. The most used DT techniques mentioned by survey participants were: interview, brainstorming, uses cases, activity analysis, user story, and rapid prototyping, whereas for creativity techniques were: analogies, creativity workshops, focus group, questions list, clarification, none and combining ideas. Conclusions: The results showed that despite the existence of a large number of techniques in the literature, the developers’ lack of knowledge about these techniques makes them not used in the industry. However, the developers’ responses showed that the use of C&DT techniques helps to make requirements elicitation more effective.