Despite the advances made by modern parsing strategies such as PEG, LL(*), GLR, and GLL, parsing is not a solved problem. Existing approaches suffer from a number of weaknesses, including difficulties supporting side-effecting embedded actions, slow and/or unpredictable performance, and counter-intuitive matching strategies. This paper introduces the ALL(*) parsing strategy that combines the simplicity, efficiency, and predictability of conventional top-down LL(k) parsers with the power of a GLR-like mechanism to make parsing decisions. The critical innovation is to move grammar analysis to parse-time, which lets ALL(*) handle any non-left-recursive context-free grammar. ALL(*) is O(n4) in theory but consistently performs linearly on grammars used in practice, outperforming general strategies such as GLL and GLR by orders of magnitude. ANTLR 4 generates ALL(*) parsers and supports direct left-recursion through grammar rewriting. Widespread ANTLR 4 use (5000 downloads/month in 2013) provides evidence that ALL(*) is effective for a wide variety of applications.

Modern IDEs make many software engineering tasks easier by automating functionality such as code completion and navigation. However, this functionality operates on one version of the code at a time. We envision a new approach that makes code completion and navigation aware of code evolution and enables them to operate on multiple versions at a time, without having to manually switch across these versions. We illustrate our approach on several example scenarios. We also describe a prototype Eclipse plugin that embodies our approach for code completion and navigation for Java code. We believe our approach opens a new line of research that adds a novel, temporal dimension for treating code in IDEs in the context of tasks that previously required manual switching across different code versions.