are webscraper static or dynamic parsers

Swapping between the stream range/iterator and the file_vector range/iterator is now controlled by defining USE_MMAP, without needing to change the source code. The combinator parser with stream iterator is now about twice the speed of the simple recursive descent parser, and the iterator interface can be used with the File-Vector which doubles the performance again. Since there are only a small number of short variable names, and programmers share habits about naming. One of the basic reasons of scoping is to keep variables in different parts of program distinct from one another. The library now uses an Iterator and Range pair, and provides a stream_range that makes backtracking much neater in the implementation, results in a 25% performance improvement compared to the pre-iterator version on non-backtracking parsers, and even more (40% improvement) on backtracking parsers. The scope of a variable x is the region of the program in which uses of x refers to its declaration. Because the combinators are implemented as static template function-objects, they can be inlined by the compiler, which results in performance better than the simple recursive-descent parser, combined with more readable and maintainable code.

This gives the programmer control over whether polymorphism is static or dynamic, and allows optimal run-time performance. However higher level parser combinators can also be implemented that take parser-handles as their arguments. The library design ensures that all combinator composition occurs at compile time, with a special construct (a parser-handle) used to allow dynamic runtime polymorphism at specific points.Īs backtraking is supported, parsers can generally consist of a set of independent static parse rules, and a single parser-handle to enable polymorphic recursion. 1.1 Dynamic grammar analysis In this paper, we introduce Adaptive LL(), or ALL(), parsers that combine the simplicity of deterministic top-down parsers with the power of a GLR-like mechanism to make parsing de-cisions. If there is only single-character look-ahead failed parsers do not consume characters, and so backtracking is unnecessary, and the state does not need to be copyable.Ī high performance C++ parser combinator library, focusing static instantiation of combinators, which differentiates it from other libraries such as Boost.Spirit. The 'attempt' parser combinator deals with saving the current result and state and restoring it on backtracking, but this relies on the state being copyable. This needs some care to interact with backtracking, as the state needs to be backtracked as well. The latest version now supports functionality equivalent to an attribute grammar, where the parser result (synthesized attribute) is returned bottom up, and state (inherited attribute) is threaded trough the parsers accumulating values left-to-right.

Are webscraper static or dynamic parsers