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Bottom-up parse tree built in numbered steps. An LR parser scans and parses the input text in one forward pass over the text. The parser builds up the parse tree incrementally, bottom up, and left to right, without guessing or backtracking.
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.
A canonical LR parser (also called a LR(1) parser) is a type of bottom-up parsing algorithm used in computer science to analyze and process programming languages.It is based on the LR parsing technique, which stands for "left-to-right, rightmost derivation in reverse."
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.
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]
An LALR parser is a simplified version of a canonical LR parser. The LALR parser was invented by Frank DeRemer in his 1969 PhD dissertation, Practical Translators for LR(k) languages, [1] in his treatment of the practical difficulties at that time of implementing LR(1) parsers. He showed that the LALR parser has more language recognition power ...
The Canonical LR constructs full lookahead sets. LALR uses merge sets, that is it merges lookahead sets where the LR(0) core is the same. The SLR uses FOLLOW sets as lookahead sets which associate the right hand side of a LR(0) core to a lookahead terminal. This is a greater simplification than that in the case of LALR because many conflicts ...
The existence of multiple derivations of the same string does not suffice to indicate that the grammar is ambiguous; only multiple leftmost derivations (or, equivalently, multiple parse trees) indicate ambiguity. For example, the simple grammar S → A + A A → 0 | 1 is an unambiguous grammar for the language { 0+0, 0+1, 1+0, 1+1 }.