Search results
Results From The WOW.Com Content Network
But by convention, the LR name stands for the form of parsing invented by Donald Knuth, and excludes the earlier, less powerful precedence methods (for example Operator-precedence parser). [1] LR parsers can handle a larger range of languages and grammars than precedence parsers or top-down LL parsing . [ 3 ]
The LR(1) parser is a deterministic automaton and as such its operation is based on static state transition tables. These codify the grammar of the language it recognizes and are typically called "parsing tables". The parsing tables of the LR(1) parser are parameterized with a lookahead terminal.
An operator-precedence parser is a simple shift-reduce parser that is capable of parsing a subset of LR(1) grammars. More precisely, the operator-precedence parser can parse all LR(1) grammars where two consecutive nonterminals and epsilon never appear in the right-hand side of any rule.
In computer science, a Simple LR or SLR parser is a type of LR parser with small parse tables and a relatively simple parser generator algorithm. As with other types of LR(1) parser, an SLR parser is quite efficient at finding the single correct bottom-up parse in a single left-to-right scan over the input stream, without guesswork or backtracking.
If the parser is produced by an SLR, LR(1), or LALR LR parser generator, the programmer will often rely on the generated parser feature of preferring shift over reduce whenever there is a conflict. [2] Alternatively, the grammar can be rewritten to remove the conflict, at the expense of an increase in grammar size (see below).
In 1965, Donald Knuth invented the LR(k) parser and proved that there exists an LR(k) grammar for every deterministic context-free language. [5] This parser still required a lot of memory. In 1969 Frank DeRemer invented the LALR and Simple LR parsers, both based on the LR parser and having greatly reduced memory requirements at the cost of less ...
A shift-reduce parser is a class of efficient, table-driven bottom-up parsing methods for computer languages and other notations formally defined by a grammar.The parsing methods most commonly used for parsing programming languages, LR parsing and its variations, are shift-reduce methods. [1]
A grammar is said to be SLR(1) if the following simple LR parser algorithm results in no ambiguity. If state s contains any item of the form A → a • Xb , where X is a terminal, and X is the next token in the input string, then the action is to shift the current input token onto the stack, and the new state to be pushed on the stack is the ...