In computer science, an LR parser is a parser for source code written in a computer language that reads input from Left to right and produces a Rightmost derivation. The term LR(k) parser is also used; where the k refers to the number of unconsumed "look ahead" input symbols that are used in making parsing decisions. Usually k is 1 and is often omitted.
The syntax of many programming languages can be defined by a grammar that is LR, or close to being so, and for this reason LR parsers are often used by compilers to perform syntax analysis of source code.

An LR Parser is a recursive program that can be proven correct by direct computation, and can be implemented more efficiently (in time) as a recursive ascent parser, a set of mutually-recursive functions for every grammar, much like a recursive descent parser. Conventionally, however, LR parsers are presented and implemented as table-based stack machines in which the call stack of the underlying recursive program is explicitly manipulated

For Example:
n m n
A=[1 (234) 5 6 ]

LR parsers are difficult to produce by hand and they are usually constructed by a parser generator or a compiler-compiler. Depending on how the parsing table is generated, these parsers can be called simple LR parsers (SLR), look-ahead LR parsers (LALR), or canonical LR parsers. LALR parsers have more language recognition power than SLR parsers. Canonical LR parsers have more recognition power than LALR parsers.

numbers= Console.ReadLine()

char[] pile = new char[numbers.Length + 2];
            char[] piles = new char[numbers.Length + 2];
            char[] enter = new char[numbers.Length + 1];

It is usually not possible to characterize the state of the parser with a single item because it may not know in advance which rule it is going to use for reduction. For example if there is also a rule E → E * B then the items E → E • + B and E → E • * B will both apply after a string corresponding with E has been read. Therefore we will characterize the state of the parser by a set of items, in this case the set { E → E • + B, E → E • * B }.

pile[0] = '#';
            char i = 1;
            for (a = 0, i = 1; A1 < numbers.Length; a++, i++)
                pile[i] = once[a];

Parsing is also an earlier term for the diagramming of sentences of natural languages, and is still used for the diagramming of inflected languages, such as the Romance languages or Latin. The term parsing comes from Latin pars meaning part

You gotta repeat this in the new pile

for (j= 0; j <= (k- 1); j++)
                            piles[i] = pile[i];
                        piles[k] = numbers[0];
                        for (i = k + 1; i < endingpart; i++)
                        piles[i] = pile[i + 2];
                        endingpart = endingpart - printing.Length + 1;
                        pile = piles; k++;

The most common use of a parser is as a component of a compiler or interpreter. This parses the source code of a computer programming language to create some form of internal representation. Programming languages tend to be specified in terms of a context-free grammar because fast and efficient parsers can be written for them. Parsers are written by hand or generated by parser generators.
The next stage is parsing or syntactic analysis, which is checking that the tokens form an allowable expression. This is usually done with reference to a context-free grammar which recursively defines components that can make up an expression and the order in which they must appear. However, not all rules defining programming languages can be expressed by context-free grammars alone, for example type validity and proper declaration of identifiers. These rules can be formally expressed with attribute grammars.

This way you will be able to construct your LR parser with any kind of gramathics.

It will be finished in other time, so I hope that this will help you.


Edited 7 Years Ago by peter_budo: Keep It Organized - For easy readability, always wrap programming code within posts in [code] (code blocks)

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