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A predictive parser is a recursive descent parser that does not require backtracking. [3] Predictive parsing is possible only for the class of LL( k ) grammars, which are the context-free grammars for which there exists some positive integer k that allows a recursive descent parser to decide which production to use by examining only the next k ...
The Spirit Parser Framework is an object oriented recursive descent parser generator framework implemented using template metaprogramming techniques. Expression templates allow users to approximate the syntax of extended Backus–Naur form (EBNF) completely in C++.
Memoization has also been used in other contexts (and for purposes other than speed gains), such as in simple mutually recursive descent parsing. [1] It is a type of caching , distinct from other forms of caching such as buffering and page replacement .
In computer programming, a parser combinator is a higher-order function that accepts several parsers as input and returns a new parser as its output. In this context, a parser is a function accepting strings as input and returning some structure as output, typically a parse tree or a set of indices representing locations in the string where parsing stopped successfully.
Common examples include algorithms on trees, and recursive descent parsers. As with direct recursion, tail call optimization is necessary if the recursion depth is large or unbounded, such as using mutual recursion for multitasking. Note that tail call optimization in general (when the function called is not the same as the original function ...
If a language grammar has multiple rules that may start with the same leftmost symbols but have different endings, then that grammar can be efficiently handled by a deterministic bottom-up parse but cannot be handled top-down without guesswork and backtracking. So bottom-up parsers in practice handle a somewhat larger range of computer language ...
Backtracking is the process of traversing the tree in preorder, depth first. Any systematic rule for choosing column c in this procedure will find all solutions, but some rules work much better than others. To reduce the number of iterations, Knuth suggests that the column-choosing algorithm select a column with the smallest number of 1s in it.
The algorithm that is presented here does not need an explicit stack; instead, it uses recursive calls to implement the stack. The algorithm is not a pure operator-precedence parser like the Dijkstra shunting yard algorithm. It assumes that the primary nonterminal is parsed in a separate subroutine, like in a recursive descent parser.