LRparsers
LR parsers are a family of deterministic bottom-up parsers for context-free grammars. The LR acronym stands for Left-to-right input scanning and Rightmost derivation in reverse. They parse by reading the input tokens left to right and constructing a rightmost derivation of the input in reverse, using a pushdown automaton implemented as a parsing table and a stack of states. LR parsing is designed for grammars that are LR, meaning a deterministic parse is possible without backtracking.
In operation, the parser maintains two stacks: a stack of grammar symbols and a stack of parsing
Variants of LR parsers differ in how much lookahead they use and how parsing tables are constructed.
History and usage: LR parsing was advanced by Frank DeRemer in the 1960s and has become foundational