Syntax analysis is the second phase of compiler design after lexical analysis. The parser checks if the input string follows the rules and structure of the formal grammar. It builds a parse tree to represent the syntactic structure. If the input string can be derived from the parse tree using the grammar, it is syntactically correct. Otherwise, an error is reported. Parsers use various techniques like panic-mode, phrase-level, and global correction to handle syntax errors and attempt to continue parsing. Context-free grammars are commonly used with productions defining the syntax rules. Derivations show the step-by-step application of productions to generate the input string from the start symbol.
The document discusses lexical analysis in compilers. It describes how the lexical analyzer reads source code characters and divides them into tokens. Regular expressions are used to specify patterns for token recognition. The lexical analyzer generates a finite state automaton to recognize these patterns. Lexical analysis is the first phase of compilation that separates the input into tokens for the parser.
The document discusses syntax analysis and parsing. It defines a syntax analyzer as creating the syntactic structure of a source program in the form of a parse tree. A syntax analyzer, also called a parser, checks if a program satisfies the rules of a context-free grammar and produces the parse tree if it does, or error messages otherwise. It describes top-down and bottom-up parsing methods and how parsers use grammars to analyze syntax.
This document discusses syntax analysis in compiler design. It begins by explaining that the lexer takes a string of characters as input and produces a string of tokens as output, which is then input to the parser. The parser takes the string of tokens and produces a parse tree of the program. Context-free grammars are introduced as a natural way to describe the recursive structure of programming languages. Derivations and parse trees are discussed as ways to parse strings based on a grammar. Issues like ambiguity and left recursion in grammars are covered, along with techniques like left factoring that can be used to transform grammars.
This document discusses parsing and syntax analysis. It provides three key points:
1. Parsing involves recognizing the structure of a program or document by constructing a parse tree. This tree represents the structure and is used to guide translation.
2. During compilation, the parser uses a grammar to check the structure of tokens produced by the lexical analyzer. It produces a parse tree and handles syntactic errors and recovery.
3. Parsers are responsible for identifying and handling syntax errors. They must detect errors efficiently and recover in a way that issues clear messages and allows processing to continue without significantly slowing down.
The document discusses the different phases of a compiler:
1. Lexical analysis scans source code as characters and converts them into tokens.
2. Syntax analysis checks token arrangements against the grammar to ensure syntactic correctness.
3. Semantic analysis checks that rules like type compatibility are followed.
4. Intermediate code is generated for an abstract machine.
5. Code optimization removes unnecessary code and improves efficiency.
6. Code generation translates the optimized intermediate code to machine language.
The document discusses the role and implementation of a lexical analyzer in compilers. A lexical analyzer is the first phase of a compiler that reads source code characters and generates a sequence of tokens. It groups characters into lexemes and determines the tokens based on patterns. A lexical analyzer may need to perform lookahead to unambiguously determine tokens. It associates attributes with tokens, such as symbol table entries for identifiers. The lexical analyzer and parser interact through a producer-consumer relationship using a token buffer.
The document discusses the role and process of a lexical analyzer in compiler design. A lexical analyzer groups input characters into lexemes and produces a sequence of tokens as output for the syntactic analyzer. It strips out comments and whitespace, correlates line numbers with errors, and interacts with the symbol table. Lexical analysis improves compiler efficiency, portability, and allows for simpler parser design by separating lexical and syntactic analysis.
The document discusses lexical analysis in compilers. It describes how the lexical analyzer reads source code characters and divides them into tokens. Regular expressions are used to specify patterns for token recognition. The lexical analyzer generates a finite state automaton to recognize these patterns. Lexical analysis is the first phase of compilation that separates the input into tokens for the parser.
The document discusses syntax analysis and parsing. It defines a syntax analyzer as creating the syntactic structure of a source program in the form of a parse tree. A syntax analyzer, also called a parser, checks if a program satisfies the rules of a context-free grammar and produces the parse tree if it does, or error messages otherwise. It describes top-down and bottom-up parsing methods and how parsers use grammars to analyze syntax.
This document discusses syntax analysis in compiler design. It begins by explaining that the lexer takes a string of characters as input and produces a string of tokens as output, which is then input to the parser. The parser takes the string of tokens and produces a parse tree of the program. Context-free grammars are introduced as a natural way to describe the recursive structure of programming languages. Derivations and parse trees are discussed as ways to parse strings based on a grammar. Issues like ambiguity and left recursion in grammars are covered, along with techniques like left factoring that can be used to transform grammars.
This document discusses parsing and syntax analysis. It provides three key points:
1. Parsing involves recognizing the structure of a program or document by constructing a parse tree. This tree represents the structure and is used to guide translation.
2. During compilation, the parser uses a grammar to check the structure of tokens produced by the lexical analyzer. It produces a parse tree and handles syntactic errors and recovery.
3. Parsers are responsible for identifying and handling syntax errors. They must detect errors efficiently and recover in a way that issues clear messages and allows processing to continue without significantly slowing down.
The document discusses the different phases of a compiler:
1. Lexical analysis scans source code as characters and converts them into tokens.
2. Syntax analysis checks token arrangements against the grammar to ensure syntactic correctness.
3. Semantic analysis checks that rules like type compatibility are followed.
4. Intermediate code is generated for an abstract machine.
5. Code optimization removes unnecessary code and improves efficiency.
6. Code generation translates the optimized intermediate code to machine language.
The document discusses the role and implementation of a lexical analyzer in compilers. A lexical analyzer is the first phase of a compiler that reads source code characters and generates a sequence of tokens. It groups characters into lexemes and determines the tokens based on patterns. A lexical analyzer may need to perform lookahead to unambiguously determine tokens. It associates attributes with tokens, such as symbol table entries for identifiers. The lexical analyzer and parser interact through a producer-consumer relationship using a token buffer.
The document discusses the role and process of a lexical analyzer in compiler design. A lexical analyzer groups input characters into lexemes and produces a sequence of tokens as output for the syntactic analyzer. It strips out comments and whitespace, correlates line numbers with errors, and interacts with the symbol table. Lexical analysis improves compiler efficiency, portability, and allows for simpler parser design by separating lexical and syntactic analysis.
The document discusses symbol tables, which are data structures used by compilers to track semantic information about identifiers, variables, functions, classes, etc. It provides details on:
- How various compiler phases like lexical analysis, syntax analysis, semantic analysis, code generation utilize and update the symbol table.
- Common data structures used to implement symbol tables like linear lists, hash tables and how they work.
- The information typically stored for different symbols like name, type, scope, memory location etc.
- Organization of symbol tables for block-structured vs non-block structured languages, including using multiple nested tables vs a single global table.
The document discusses different types of parsing including:
1) Top-down parsing which starts at the root node and builds the parse tree recursively, requiring backtracking for ambiguous grammars.
2) Bottom-up parsing which starts at the leaf nodes and applies grammar rules in reverse to reach the start symbol using shift-reduce parsing.
3) LL(1) and LR parsing which are predictive parsing techniques using parsing tables constructed from FIRST and FOLLOW sets to avoid backtracking.
This document provides an introduction to finite automata. It defines key concepts like alphabets, strings, languages, and finite state machines. It also describes the different types of automata, specifically deterministic finite automata (DFAs) and nondeterministic finite automata (NFAs). DFAs have a single transition between states for each input, while NFAs can have multiple transitions. NFAs are generally easier to construct than DFAs. The next class will focus on deterministic finite automata in more detail.
This document provides an overview of syntax analysis in compiler design. It discusses context free grammars, derivations, parse trees, ambiguity, and various parsing techniques. Top-down parsing approaches like recursive descent parsing and LL(1) parsing are described. Bottom-up techniques including shift-reduce parsing and operator precedence parsing are also introduced. The document provides examples and practice problems related to grammar rules, derivations, parse trees, and eliminating ambiguity.
The document discusses the pumping lemma for regular sets. It states that for any regular language L, there exists a constant n such that any string w in L of length at least n can be broken down into sections xyz such that y is not empty, xy is less than or equal to n, and xykz is in L for all k. The pumping lemma can be used to show a language is not regular by finding a string that does not satisfy the lemma conditions. Examples are provided to demonstrate how to use the pumping lemma to prove languages are not regular.
The document discusses compilers and their role in translating high-level programming languages into machine-readable code. It notes that compilers perform several key functions: lexical analysis, syntax analysis, generation of an intermediate representation, optimization of the intermediate code, and finally generation of assembly or machine code. The compiler allows programmers to write code in a high-level language that is easier for humans while still producing efficient low-level code that computers can execute.
Lexical analysis is the first phase of compilation. It reads source code characters and divides them into tokens by recognizing patterns using finite automata. It separates tokens, inserts them into a symbol table, and eliminates unnecessary characters. Tokens are passed to the parser along with line numbers for error handling. An input buffer is used to improve efficiency by reading source code in blocks into memory rather than character-by-character from secondary storage. Lexical analysis groups character sequences into lexemes, which are then classified as tokens based on patterns.
Loop optimization is a technique to improve the performance of programs by optimizing the inner loops which take a large amount of time. Some common loop optimization methods include code motion, induction variable and strength reduction, loop invariant code motion, loop unrolling, and loop fusion. Code motion moves loop-invariant code outside the loop to avoid unnecessary computations. Induction variable and strength reduction techniques optimize computations involving induction variables. Loop invariant code motion avoids repeating computations inside loops. Loop unrolling replicates loop bodies to reduce loop control overhead. Loop fusion combines multiple nested loops to reduce the total number of iterations.
The document discusses operator precedence parsing, which is a bottom-up parsing technique for operator grammars. It describes operator precedence grammars as grammars where no RHS has a non-terminal and no two non-terminals are adjacent. An operator precedence parser uses a parsing table to shift or reduce based on the precedence relations between terminals. It provides an example of constructing a precedence parsing table and parsing a string using the operator precedence parsing algorithm.
The document discusses finite automata including nondeterministic finite automata (NFAs) and deterministic finite automata (DFAs). It provides examples of NFAs and DFAs that recognize particular strings, including strings containing certain substrings. It also gives examples of DFA state machines and discusses using finite automata to recognize regular languages.
1) LR(0) parsers use left-to-right, rightmost derivations with 0-token lookahead to parse context-free grammars deterministically.
2) The states of the LR(0) automaton are sets of parsing items that indicate the progress of recognizing productions.
3) Parsing tables are constructed from the automaton to specify the shift and reduce actions and state transitions based on the next input symbol.
This slide is prepared By these following Students of Dept. of CSE JnU, Dhaka. Thanks To: Nusrat Jahan, Arifatun Nesa, Fatema Akter, Maleka Khatun, Tamanna Tabassum.
This document provides an introduction to compilers, including:
- What compilers are and their role in translating programs to machine code
- The main phases of compilation: lexical analysis, syntax analysis, semantic analysis, code generation, and optimization
- Key concepts like tokens, parsing, symbol tables, and intermediate representations
- Related software tools like preprocessors, assemblers, loaders, and linkers
This document discusses syntax-directed translation, which refers to a method of compiler implementation where the source language translation is completely driven by the parser. The parsing process and parse trees are used to direct semantic analysis and translation of the source program. Attributes and semantic rules are associated with the grammar symbols and productions to control semantic analysis and translation. There are two main representations of semantic rules: syntax-directed definitions and syntax-directed translation schemes. Syntax-directed translation schemes embed program fragments called semantic actions within production bodies and are more efficient than syntax-directed definitions as they indicate the order of evaluation of semantic actions. Attribute grammars can be used to represent syntax-directed translations.
This document provides an overview of syntax-directed translation and attribute grammars. It discusses:
- Syntax-directed definitions associate semantic rules with production rules to evaluate attributes and perform actions like code generation. Attributes can represent various types of information.
- Syntax trees can be annotated with attribute values. The order attributes are computed depends on semantic rule dependencies.
- Translation schemes specify an order for evaluating semantic actions associated with productions. This provides implementation details omitted from syntax-directed definitions.
- S-attributed and L-attributed definitions are subclasses that allow efficient single-pass evaluation during parsing by restricting how attributes can be used.
This document discusses compiler design and how compilers work. It begins with prerequisites and definitions of compilers and their origins. It then describes the architecture of compilers, including lexical analysis, parsing, semantic analysis, code optimization, and code generation. It explains how compilers translate high-level code into machine-executable code. In conclusions, it summarizes that compilers translate code without changing meaning and aim to make code efficient. References for further reading on compiler design principles are also provided.
Token, Pattern and Lexeme defines some key concepts in lexical analysis:
Tokens are valid sequences of characters that can be identified as keywords, constants, identifiers, numbers, operators or punctuation. A lexeme is the sequence of characters that matches a token pattern. Patterns are defined by regular expressions or grammar rules to identify lexemes as specific tokens. The lexical analyzer collects attributes like values for number tokens and symbol table entries for identifiers and passes the tokens and attributes to the parser. Lexical errors occur if a character sequence cannot be scanned as a valid token. Error recovery strategies include deleting or inserting characters to allow tokenization to continue.
A compiler acts as a translator that converts programs written in high-level human-readable languages into machine-readable low-level languages. Compilers are needed because computers can only understand machine languages, not human languages. A compiler performs analysis and synthesis on a program, breaking the process into phases like scanning, parsing, code generation, and optimization to translate the high-level code into an executable form. The phases include lexical analysis, syntax analysis, semantic analysis, code generation, and optimization.
LEX is a tool that allows users to specify a lexical analyzer by defining patterns for tokens using regular expressions. The LEX compiler transforms these patterns into a transition diagram and generates C code. It takes a LEX source program as input, compiles it to produce lex.yy.c, which is then compiled with a C compiler to generate an executable that takes an input stream and returns a sequence of tokens. LEX programs have declarations, translation rules that map patterns to actions, and optional auxiliary functions. The actions are fragments of C code that execute when a pattern is matched.
8-Practice problems on operator precedence parser-24-05-2023.docxvenkatapranaykumarGa
The document discusses various topics related to syntax analysis in compilers including:
1. The role of the parser is to verify the structure of tokens based on the grammar and construct a parse tree while reporting any errors.
2. Context-free grammars are used to describe the syntactic structure of programming languages and consist of terminals, non-terminals, a start symbol, and productions.
3. Parsing involves analyzing input to determine its structure according to a grammar, which can be done using top-down or bottom-up parsing methods. Top-down methods include recursive descent and predictive parsing.
The document discusses symbol tables, which are data structures used by compilers to track semantic information about identifiers, variables, functions, classes, etc. It provides details on:
- How various compiler phases like lexical analysis, syntax analysis, semantic analysis, code generation utilize and update the symbol table.
- Common data structures used to implement symbol tables like linear lists, hash tables and how they work.
- The information typically stored for different symbols like name, type, scope, memory location etc.
- Organization of symbol tables for block-structured vs non-block structured languages, including using multiple nested tables vs a single global table.
The document discusses different types of parsing including:
1) Top-down parsing which starts at the root node and builds the parse tree recursively, requiring backtracking for ambiguous grammars.
2) Bottom-up parsing which starts at the leaf nodes and applies grammar rules in reverse to reach the start symbol using shift-reduce parsing.
3) LL(1) and LR parsing which are predictive parsing techniques using parsing tables constructed from FIRST and FOLLOW sets to avoid backtracking.
This document provides an introduction to finite automata. It defines key concepts like alphabets, strings, languages, and finite state machines. It also describes the different types of automata, specifically deterministic finite automata (DFAs) and nondeterministic finite automata (NFAs). DFAs have a single transition between states for each input, while NFAs can have multiple transitions. NFAs are generally easier to construct than DFAs. The next class will focus on deterministic finite automata in more detail.
This document provides an overview of syntax analysis in compiler design. It discusses context free grammars, derivations, parse trees, ambiguity, and various parsing techniques. Top-down parsing approaches like recursive descent parsing and LL(1) parsing are described. Bottom-up techniques including shift-reduce parsing and operator precedence parsing are also introduced. The document provides examples and practice problems related to grammar rules, derivations, parse trees, and eliminating ambiguity.
The document discusses the pumping lemma for regular sets. It states that for any regular language L, there exists a constant n such that any string w in L of length at least n can be broken down into sections xyz such that y is not empty, xy is less than or equal to n, and xykz is in L for all k. The pumping lemma can be used to show a language is not regular by finding a string that does not satisfy the lemma conditions. Examples are provided to demonstrate how to use the pumping lemma to prove languages are not regular.
The document discusses compilers and their role in translating high-level programming languages into machine-readable code. It notes that compilers perform several key functions: lexical analysis, syntax analysis, generation of an intermediate representation, optimization of the intermediate code, and finally generation of assembly or machine code. The compiler allows programmers to write code in a high-level language that is easier for humans while still producing efficient low-level code that computers can execute.
Lexical analysis is the first phase of compilation. It reads source code characters and divides them into tokens by recognizing patterns using finite automata. It separates tokens, inserts them into a symbol table, and eliminates unnecessary characters. Tokens are passed to the parser along with line numbers for error handling. An input buffer is used to improve efficiency by reading source code in blocks into memory rather than character-by-character from secondary storage. Lexical analysis groups character sequences into lexemes, which are then classified as tokens based on patterns.
Loop optimization is a technique to improve the performance of programs by optimizing the inner loops which take a large amount of time. Some common loop optimization methods include code motion, induction variable and strength reduction, loop invariant code motion, loop unrolling, and loop fusion. Code motion moves loop-invariant code outside the loop to avoid unnecessary computations. Induction variable and strength reduction techniques optimize computations involving induction variables. Loop invariant code motion avoids repeating computations inside loops. Loop unrolling replicates loop bodies to reduce loop control overhead. Loop fusion combines multiple nested loops to reduce the total number of iterations.
The document discusses operator precedence parsing, which is a bottom-up parsing technique for operator grammars. It describes operator precedence grammars as grammars where no RHS has a non-terminal and no two non-terminals are adjacent. An operator precedence parser uses a parsing table to shift or reduce based on the precedence relations between terminals. It provides an example of constructing a precedence parsing table and parsing a string using the operator precedence parsing algorithm.
The document discusses finite automata including nondeterministic finite automata (NFAs) and deterministic finite automata (DFAs). It provides examples of NFAs and DFAs that recognize particular strings, including strings containing certain substrings. It also gives examples of DFA state machines and discusses using finite automata to recognize regular languages.
1) LR(0) parsers use left-to-right, rightmost derivations with 0-token lookahead to parse context-free grammars deterministically.
2) The states of the LR(0) automaton are sets of parsing items that indicate the progress of recognizing productions.
3) Parsing tables are constructed from the automaton to specify the shift and reduce actions and state transitions based on the next input symbol.
This slide is prepared By these following Students of Dept. of CSE JnU, Dhaka. Thanks To: Nusrat Jahan, Arifatun Nesa, Fatema Akter, Maleka Khatun, Tamanna Tabassum.
This document provides an introduction to compilers, including:
- What compilers are and their role in translating programs to machine code
- The main phases of compilation: lexical analysis, syntax analysis, semantic analysis, code generation, and optimization
- Key concepts like tokens, parsing, symbol tables, and intermediate representations
- Related software tools like preprocessors, assemblers, loaders, and linkers
This document discusses syntax-directed translation, which refers to a method of compiler implementation where the source language translation is completely driven by the parser. The parsing process and parse trees are used to direct semantic analysis and translation of the source program. Attributes and semantic rules are associated with the grammar symbols and productions to control semantic analysis and translation. There are two main representations of semantic rules: syntax-directed definitions and syntax-directed translation schemes. Syntax-directed translation schemes embed program fragments called semantic actions within production bodies and are more efficient than syntax-directed definitions as they indicate the order of evaluation of semantic actions. Attribute grammars can be used to represent syntax-directed translations.
This document provides an overview of syntax-directed translation and attribute grammars. It discusses:
- Syntax-directed definitions associate semantic rules with production rules to evaluate attributes and perform actions like code generation. Attributes can represent various types of information.
- Syntax trees can be annotated with attribute values. The order attributes are computed depends on semantic rule dependencies.
- Translation schemes specify an order for evaluating semantic actions associated with productions. This provides implementation details omitted from syntax-directed definitions.
- S-attributed and L-attributed definitions are subclasses that allow efficient single-pass evaluation during parsing by restricting how attributes can be used.
This document discusses compiler design and how compilers work. It begins with prerequisites and definitions of compilers and their origins. It then describes the architecture of compilers, including lexical analysis, parsing, semantic analysis, code optimization, and code generation. It explains how compilers translate high-level code into machine-executable code. In conclusions, it summarizes that compilers translate code without changing meaning and aim to make code efficient. References for further reading on compiler design principles are also provided.
Token, Pattern and Lexeme defines some key concepts in lexical analysis:
Tokens are valid sequences of characters that can be identified as keywords, constants, identifiers, numbers, operators or punctuation. A lexeme is the sequence of characters that matches a token pattern. Patterns are defined by regular expressions or grammar rules to identify lexemes as specific tokens. The lexical analyzer collects attributes like values for number tokens and symbol table entries for identifiers and passes the tokens and attributes to the parser. Lexical errors occur if a character sequence cannot be scanned as a valid token. Error recovery strategies include deleting or inserting characters to allow tokenization to continue.
A compiler acts as a translator that converts programs written in high-level human-readable languages into machine-readable low-level languages. Compilers are needed because computers can only understand machine languages, not human languages. A compiler performs analysis and synthesis on a program, breaking the process into phases like scanning, parsing, code generation, and optimization to translate the high-level code into an executable form. The phases include lexical analysis, syntax analysis, semantic analysis, code generation, and optimization.
LEX is a tool that allows users to specify a lexical analyzer by defining patterns for tokens using regular expressions. The LEX compiler transforms these patterns into a transition diagram and generates C code. It takes a LEX source program as input, compiles it to produce lex.yy.c, which is then compiled with a C compiler to generate an executable that takes an input stream and returns a sequence of tokens. LEX programs have declarations, translation rules that map patterns to actions, and optional auxiliary functions. The actions are fragments of C code that execute when a pattern is matched.
8-Practice problems on operator precedence parser-24-05-2023.docxvenkatapranaykumarGa
The document discusses various topics related to syntax analysis in compilers including:
1. The role of the parser is to verify the structure of tokens based on the grammar and construct a parse tree while reporting any errors.
2. Context-free grammars are used to describe the syntactic structure of programming languages and consist of terminals, non-terminals, a start symbol, and productions.
3. Parsing involves analyzing input to determine its structure according to a grammar, which can be done using top-down or bottom-up parsing methods. Top-down methods include recursive descent and predictive parsing.
This document discusses syntax analysis and parsing. It introduces context-free grammars and how they are used to specify the syntax of programming languages. There are two main types of parsing: top-down parsing which builds the parse tree from the root going down, and bottom-up parsing which builds up the tree from the leaves to the root. Specific parsing algorithms like recursive descent and LR parsing are also introduced.
This document describes the syllabus for the course CS2352 Principles of Compiler Design. It includes 5 units covering lexical analysis, syntax analysis, intermediate code generation, code generation, and code optimization. The objectives of the course are to understand and implement a lexical analyzer, parser, code generation schemes, and optimization techniques. It lists a textbook and references for the course and provides a brief description of the topics to be covered in each unit.
The document contains questions and answers related to compiler design topics such as parsing, grammars, syntax analysis, error handling, derivation, sentential forms, parse trees, ambiguity, left and right recursion elimination etc. Key points discussed are:
1. The role of parser is to verify the string of tokens generated by lexical analyzer according to the grammar rules and detect syntax errors. It outputs a parse tree.
2. Common parsing methods are top-down, bottom-up and universal. Top-down methods include LL, LR. Bottom-up methods include LR, LALR.
3. Errors can be lexical, syntactic, semantic and logical detected by different compiler phases. Error recovery strategies include panic mode
This document discusses context-free grammars and parsing. It defines context-free grammars and how they are used to specify the syntactic structure of programming languages. Key points include:
- Context-free grammars use recursive rules and regular expressions to define a language's syntax.
- Parsing involves using a context-free grammar to derive a syntax tree from a sequence of tokens.
- Derivations show how strings of tokens are generated from a grammar's start symbol through replacements.
- The language defined by a grammar consists of all strings that can be derived from the start symbol.
There are several types of errors that can occur in programs, including lexical errors, syntactic errors, semantic errors, and logical errors. Error handling functions should clearly report errors, recover from errors quickly, and not slow down processing of correct programs. When parsing code, common recovery strategies include panic mode recovery, phrase level recovery, using error productions, and global correction. Universal parsers and top-down/bottom-up parsers are different techniques used for parsing grammars. Context-free grammars are commonly used to specify the structure of programming languages.
This document discusses parsing methods and techniques for high performance computing. It covers the following key points in 3 sentences:
The document outlines the various phases of compiler design including lexical analysis, syntax analysis, semantic analysis, code generation, and optimization. It then discusses parsing in more detail, describing lexical analysis as the first phase that interacts with source code to generate tokens, and syntax analysis/parsing as taking tokens to build parse trees according to grammar rules. The document also covers different parsing techniques like top-down and bottom-up parsing, and issues around implementing parallel parsing such as dividing code, synchronization, processor allocation, threading, task distribution, and context switching.
The document discusses the role of the parser in compiler design. It explains that the parser takes a stream of tokens from the lexical analyzer and checks if the source program satisfies the rules of the context-free grammar. If so, it creates a parse tree representing the syntactic structure. Parsers are categorized as top-down or bottom-up based on the direction they build the parse tree. The document also covers context-free grammars, derivations, parse trees, ambiguity, and techniques for eliminating left-recursion from grammars.
match the following attributes to the parts of a compilerstrips ou.pdfarpitaeron555
match the following attributes to the parts of a compiler
strips out the comments and whitespace
converts text into lexemes
generates an Abstrat Symbol Tree
recursive descent or table driven
uses BNF or EBNF definitions
a. lexer
b. parser
Solution
The Program and Portfolio Management Maturity Model is an effective tool for organizations to
decide quickly what PPM improvements they should make to enhance their organization\'s
ability to optimize investments, execute big changes and deliver value.
Overview
Key Findings
Real project, program and portfolio management, when operating at the level of well-integrated
practices, is the key enabler that allows organizations to identify and execute strategic change.
Any meaningful undertakings to enhance or evolve the program and portfolio management
(PPM) function must pay more than lip service to organizational structure, business model and
culture to have any chance of success.
Competitive pressures and changing market conditions are forcing organizations toward Level 3,
and most organizations still aren\'t ready to make the leap.
Recommendations
At any level of PPM maturity, focus first on helping the organization make well-informed
investment choices. This will improve the odds of project success more than any other factor.
For organizations that require enterprisewide change and capabilities, it is worth the effort to
pursue Level 4, where enterprise PPM practices are built.
Identify objectives for your enterprise, and use them to identify the most salient improvement
opportunities for your enterprise.
Meticulously manage the change involved in maturing/improving your PPM capabilities.
Analysis
Project/program/portfolio management office (PMO) leaders, program managers and portfolio
managers are frequently challenged by ineffective processes, lack of stakeholder engagement and
difficult-to-quantify value. 1 Part of the problem is failure to match their processes, people and
technology approaches to the maturity level of their organizations. 2
The Gartner Program and Portfolio Management (PPM) Maturity Model assessment is designed
to help PPM leaders understand best practices around large project management, as well as PPM
to handle delivery of strategic value. This model assumes that organizations progress through a
maturity curve and that each level of organizational maturity directly affects the level of
investment and types of PPM approaches organizations choose to adopt.
arsing
A parser is an algorithm that determines whether a given input string is in a language and, as a
side-effect, usually produces a parse tree for the input. There is a procedure for generating a
parser from a given context-free grammar.
Recursive-Descent Parsing
Recursive-descent parsing is one of the simplest parsing techniques that is used in practice.
Recursive-descent parsers are also called top-down parsers, since they construct the parse tree
top down (rather than bottom up).
The basic idea of recursive-descent par.
The role of the parser and Error recovery strategies ppt in compiler designSadia Akter
This document summarizes error recovery strategies used by parsers. It discusses the role of parsers in validating syntax based on grammars and producing parse trees. It then describes several error recovery strategies like panic-mode recovery, phrase-level recovery using local corrections, adding error productions to the grammar, and global correction aiming to make minimal changes to parse invalid inputs.
The document discusses syntax analysis in compiler design. It defines syntax analysis as the process of analyzing a string of symbols according to the rules of a formal grammar. This involves checking the syntax against a context-free grammar, which is more powerful than regular expressions and can check balancing of tokens. The output of syntax analysis is a parse tree. It separates lexical analysis and parsing for simplicity and efficiency. Lexical analysis breaks the source code into tokens, while parsing analyzes token streams against production rules to detect errors and generate the parse tree.
This document summarizes key concepts about context-free grammars and parsing from Chapter 4 of a compiler textbook. It defines context-free grammars and their components: terminals, nonterminals, a start symbol, and productions. It describes the roles of lexical analysis and parsing in a compiler. Common parsing methods like LL, LR, top-down and bottom-up are introduced. The document also discusses representing language syntax with grammars, handling syntax errors, and strategies for error recovery.
The document discusses language design issues, specifically describing syntax and formal methods for describing syntax. It covers context-free grammars, Backus-Naur Form (BNF), and how BNF can be used to formally describe the syntax of programming languages. Key concepts explained include non-terminals, terminals, production rules, derivations, parse trees, and how precedence can be handled to avoid ambiguity.
The document discusses the different phases of a compiler:
1. Lexical analysis scans source code and converts it to tokens.
2. Syntax analysis checks token arrangements against the grammar to validate syntax.
3. Semantic analysis checks that rules like type compatibility are followed.
4. Intermediate code is generated for an abstract machine.
5. Code is optimized in the intermediate representation.
6. Code generation produces machine code from the optimized intermediate code.
Cs6660 compiler design may june 2016 Answer Keyappasami
The document describes the various phases of a compiler:
1. Lexical analysis breaks the source code into tokens.
2. Syntax analysis generates a parse tree from the tokens.
3. Semantic analysis checks for semantic correctness using the parse tree and symbol table.
4. Intermediate code generation produces machine-independent code.
5. Code optimization improves the intermediate code.
6. Code generation translates the optimized code into target machine code.
A compiler is a program that translates a program written in one language (the source language) into an equivalent program in another language (the target language). The compilation process consists of two parts - analysis and synthesis. Analysis breaks down the source program into tokens, constructs the symbol table, and performs semantic analysis. Synthesis generates the target program from the intermediate representation. The front end of a compiler includes lexical analysis, syntax analysis, semantic analysis, and intermediate code generation. The back end includes code optimization, code generation, and other machine-dependent tasks. Peephole optimization is a simple and effective code improvement technique that examines short sequences of target instructions and replaces them if possible.
This document discusses Flex and Bison, which are tools for generating lexical analyzers and parsers.
Flex is used for recognizing regular expressions and dividing input streams into tokens. Bison is used for building programs that handle structured input by taking tokens from Flex and grouping them logically based on context-free grammars.
The document explains key concepts such as shift-reduce parsing, lookahead, leftmost and rightmost derivations, and how to specify grammars, tokens, types, rules and actions in a Bison specification to build a parser. It also covers ambiguity, conflicts and how precedence and associativity help resolve shift-reduce conflicts.
Similar to Syntax Analysis in Compiler Design (20)
3rd International Conference on Artificial Intelligence Advances (AIAD 2024)GiselleginaGloria
3rd International Conference on Artificial Intelligence Advances (AIAD 2024) will act as a major forum for the presentation of innovative ideas, approaches, developments, and research projects in the area advanced Artificial Intelligence. It will also serve to facilitate the exchange of information between researchers and industry professionals to discuss the latest issues and advancement in the research area. Core areas of AI and advanced multi-disciplinary and its applications will be covered during the conferences.
Determination of Equivalent Circuit parameters and performance characteristic...pvpriya2
Includes the testing of induction motor to draw the circle diagram of induction motor with step wise procedure and calculation for the same. Also explains the working and application of Induction generator
Particle Swarm Optimization–Long Short-Term Memory based Channel Estimation w...IJCNCJournal
Paper Title
Particle Swarm Optimization–Long Short-Term Memory based Channel Estimation with Hybrid Beam Forming Power Transfer in WSN-IoT Applications
Authors
Reginald Jude Sixtus J and Tamilarasi Muthu, Puducherry Technological University, India
Abstract
Non-Orthogonal Multiple Access (NOMA) helps to overcome various difficulties in future technology wireless communications. NOMA, when utilized with millimeter wave multiple-input multiple-output (MIMO) systems, channel estimation becomes extremely difficult. For reaping the benefits of the NOMA and mm-Wave combination, effective channel estimation is required. In this paper, we propose an enhanced particle swarm optimization based long short-term memory estimator network (PSOLSTMEstNet), which is a neural network model that can be employed to forecast the bandwidth required in the mm-Wave MIMO network. The prime advantage of the LSTM is that it has the capability of dynamically adapting to the functioning pattern of fluctuating channel state. The LSTM stage with adaptive coding and modulation enhances the BER.PSO algorithm is employed to optimize input weights of LSTM network. The modified algorithm splits the power by channel condition of every single user. Participants will be first sorted into distinct groups depending upon respective channel conditions, using a hybrid beamforming approach. The network characteristics are fine-estimated using PSO-LSTMEstNet after a rough approximation of channels parameters derived from the received data.
Keywords
Signal to Noise Ratio (SNR), Bit Error Rate (BER), mm-Wave, MIMO, NOMA, deep learning, optimization.
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Sri Guru Hargobind Ji - Bandi Chor Guru.pdfBalvir Singh
Sri Guru Hargobind Ji (19 June 1595 - 3 March 1644) is revered as the Sixth Nanak.
• On 25 May 1606 Guru Arjan nominated his son Sri Hargobind Ji as his successor. Shortly
afterwards, Guru Arjan was arrested, tortured and killed by order of the Mogul Emperor
Jahangir.
• Guru Hargobind's succession ceremony took place on 24 June 1606. He was barely
eleven years old when he became 6th Guru.
• As ordered by Guru Arjan Dev Ji, he put on two swords, one indicated his spiritual
authority (PIRI) and the other, his temporal authority (MIRI). He thus for the first time
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people’s freedom and independence to practice religion by choice. He transformed
Sikhs to be Saints and Soldier.
• He had a long tenure as Guru, lasting 37 years, 9 months and 3 days
An In-Depth Exploration of Natural Language Processing: Evolution, Applicatio...DharmaBanothu
Natural language processing (NLP) has
recently garnered significant interest for the
computational representation and analysis of human
language. Its applications span multiple domains such
as machine translation, email spam detection,
information extraction, summarization, healthcare,
and question answering. This paper first delineates
four phases by examining various levels of NLP and
components of Natural Language Generation,
followed by a review of the history and progression of
NLP. Subsequently, we delve into the current state of
the art by presenting diverse NLP applications,
contemporary trends, and challenges. Finally, we
discuss some available datasets, models, and
evaluation metrics in NLP.
2. Outline
Definition - Role of parser
Lexical versus Syntactic Analysis
Representative Grammars
Syntax Error Handling
Error recovery strategies
Derivations
2
3. What is Syntax Analysis?
Syntax Analysis is a second phase of the compiler design process after lexical
analysis in which the given input string is checked for the confirmation of rules and
structure of the formal grammar.
Syntax Analyzer or Parser analyses the syntactical structure and checks if the
given input is in the correct syntax of the programming language or not.
It does so by getting the input from the tokens and building a data structure, called a
Syntax tree or Parse tree.
3
5. Cont.
The parse tree is constructed by using the pre-defined Grammar of the language and
the input string.
If the given input string can be produced with the help of the syntax tree, then the
input string is found to be in the correct syntax.
Otherwise, error is reported by syntax analyzer.
5
7. Tasks performed by Parser
The parser helps to apply rules to the code
Helps to make sure that each opening brace has a corresponding closing balance
Helps to detect all types of Syntax errors
Find the position at which error has occurred
Clear and accurate description of the error
Recovery from an error to continue and find further errors in the code
Should not affect compilation of “correct” programs
The parse must reject invalid texts by reporting syntax errors
7
8. Types of Parsers
Three types:
Universal Parser
Top-down Parser
Bottom-up Parser
Universal Parsers like CYK (Cocke-Younger-Kasami) algorithm and Earley’s
Algorithm can parse any grammar but they are inefficient to use in production
compilers.
As implied by their names, top-down parsers build parse trees from the top (root) to
the bottom (leaves). Eg. LL parser
Bottom-up parsers start from the leaves and work their way up to the root. Eg. LR
parser
8
9. Syntax Error Handling
Types of Errors
1) Lexical
2) Syntactic
3) Semantic
4) Logical
Lexical errors include misspellings of identiers, keywords, or
operators.
e.g., the use of an identier elipseSize instead of ellipseSize
missing quotes around text intended as a string
Syntactic errors include misplaced semicolons or extra or
missing braces; that is, “{”or “}”
Example: In C or Java, the appearance of a case statement without
an enclosing switch is a syntactic error
9
10. Syntax Error Handling
Types of Errors
1) Lexical
2) Syntactic
3) Semantic
4) Logical
Semantic errors include type mismatches between operators and
operands,
e.g., the return of a value in a Java method with result type void.
Logical errors occur when executed code does not produce the
expected result.
incorrect reasoning on the part of the programmer
The use in a C program of the assignment operator = instead of the
comparison operator = =
10
11. Syntax Error Handling
The error handler in a parser has goals that are simple to state but
challenging to realize:
Report the presence of errors clearly and accurately.
Recover from each error quickly enough to detect subsequent errors.
Add minimal overhead to the processing of correct programs.
11
13. Panic-Mode Recovery
Once an error is found, the parser intends to find designated
set of synchronizing tokens by discarding input symbols one
at a time.
Synchronizing tokens are delimiters, semicolon or } whose
role in source program is clear.
When parser finds an error in the statement, it ignores the rest
of the statement by not processing the input.
Advantage:
Simplicity
Never get into infinite loop
Disadvantage:
Additional errors cannot be checked as some of the input
symbols will be skipped.
13
14. Phrase-Level Recovery
When a parser finds an error, it tries to take corrective
measures so that the rest of inputs of statement allow the
parser to parse ahead. The corrections may be
Replacing a prefix by some string.
Replacing comma by semicolon.
Deleting extraneous semicolon.
Inserting missing semicolon.
Advantage:
It can correct any input string.
Disadvantage:
It is difficult to cope up with actual error if it has occurred before the
point of detection.
14
15. Error Productions
The use of the error production method can be incorporated if
the user is aware of common mistakes that are encountered in
grammar in conjunction with errors that produce erroneous
constructs.
Example: write 5x instead of 5*x
Advantage:
If this is used then, during parsing appropriate error messages can be
generated and parsing can be continued.
Disadvantage:
The disadvantage is that it’s difficult to maintain.
15
16. Global Correction
The parser considers the program in hand as a whole and tries
to figure out what the program is intended to do and tries to
find out a closest match for it, which is error-free.
When an erroneous input statement X is fed, it creates a parse
tree for some closest error-free statement Y.
Advantage:
This may allow the parser to make minimal changes in the source
code.
Disadvantage:
Due to the complexity (time and space) of this strategy, it has not
been implemented in practice yet.
16
19. Representative Grammars - CFG
Context-free grammars are named as such because any of the production
rules in the grammar can be applied regardless of context—it does not
depend on any other symbols that may or may not be around a given symbol
that is having a rule applied to it.
A context free grammar G is defined by four tuple format as
G = (V, T, P, S)
where,
G − Grammar
V − Set of variables
T − Set of terminals
P − Set of productions
S − Start symbol
19
20. Context Free Grammar
Terminals are symbols from which strings are formed.
Lowercase letters, i.e., a, b, c.
Operators, i.e., +,−, ∗.
Punctuation symbols, i.e., comma, parenthesis.
Digits, i.e., 0, 1, 2, · · · ,9.
Boldface letters, i.e., id, if.
Non-terminals are syntactic variables that denote a set of strings.
Uppercase letters, i.e., A, B, C.
Lowercase italic names, i.e., expr, stmt.
Start symbol is the head of the production stated first in the grammar.
Production is of the form LHS → RHS or head → body, where head
contains only one non-terminal and body contains a collection of
terminals and non-terminals.
20
21. Context Free Grammar
Example
E → E + T | E − T | T
T → T ∗ F | T / F | F
F → (E) | id
V = {E, T, F}
T = {+ , −, *, /, ( , ), id}
S = {E}
P :
E → E+T T→ T / F
E → E−T T→ F
E →T F→ (E)
T → T∗ F F→ id
21
23. Leftmost Derivation
At each and every step the leftmost non-terminal is expanded by substituting its
corresponding production to derive a string.
E → E + E | E ∗ E | id
23
24. Rightmost Derivation
At each and every step the rightmost non-terminal is expanded by substituting its
corresponding production to derive a string.
E → E + E | E ∗ E | id
24
26. Parse Tree
• Parse tree is a hierarchical structure
which represents the derivation of the
grammar to yield input strings.
• Root node of parse tree has the start
symbol of the given grammar from
where the derivation proceeds.
• Leaves of parse tree represent terminals.
• Each interior node represents
productions of grammar.
• If G : E → E+E | E*E | ( E ) | - E | id is
the grammar, then Parse tree for the
input string - (id + id) is shown.
26
28. References
Alfred V Aho, Jeffery D Ullman, Ravi Sethi, "Compilers, Principles
techniques and tools", Pearson Education 2011
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