Gradual typing has emerged as the tonic for programmers with a thirst for a blend of static and dynamic typing. Contracts provide a lightweight form of gradual typing as they can be implemented as a library, rather than requiring a gradual type system.Intersection and union types are well suited to static and dynamic languages: intersection encodes overloaded functions; union encodes uncertain data arising from branching code. We extend the untyped lambda calculus with contracts for monitoring higher-order intersection and union types, for the first time giving a uniform treatment to both. Each operator requires a single reduction rule that does not depend on the constituent types or the context of the operator.We present a new method for defining contract satisfaction based on blame behaviour. A value positively satisfies a type if applying a contract of that type can never elicit positive blame. A continuation negatively satisfies a type if applying a contract of that type can never elicit negative blame. We supplement our definition of satisfaction with a series of monitoring properties that satisfying values and continuations should have.
We report results from a survey on spreadsheet use and experience with textual programming languages (n = 49). We find significant correlations between self-reported formula experience, programming experience, and overall spreadsheet experience. We discuss the implications of our findings for spreadsheet research and end-user programming research, more generally.
The value of computational abstractions to nonexpert end-user programmers is contentious. We study reactions to the LAMBDA function in Microsoft Excel, which enables users to define their own functions using the spreadsheet formula language, through a thematic analysis of nearly 2,700 comments posted on the Reddit, Hacker News, YouTube, and Microsoft Tech Community online forums. We find that computational abstractions are viewed both as helpful and harmful, that users encounter learning and understanding barriers to applying them, and that there are deficiencies and opportunities in tooling such as in formula editing, versioning, reuse and sharing. We find that the introduction of LAMBDA prompts new debate around whether spreadsheets are code, whether writing formulas can be considered programming, and whether spreadsheet users identify themselves as programmers.
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