A LR parser is called a shift-reduce algorithm, because in most cases it either shifts the next lexeme of input onto the parse stack or reduces the handle that is on top of the stack.
Explanation:
A parser is that aspect of the compiler which practices a token string as input and with the sustenance of enduring grammar, transforms it into the identical parse tree. The LR parser is a non-recursive, shift-reduce, bottom-up parser. It utilizes a broad range of context-free grammar which gives it the most valuable syntax analysis procedure.
LR means that the data is examined left-to-right and that a rightmost source, in reverse, is assembled. LR parsers relish time and space extended in the size of the input. Practically all programming languages possess LR grammars.
