Designing LR(O) Parser Part-4

Duration: 7 min

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Module outline

  1. About Course: UPPSC Course Overview
  2. Interview Preparation & Guidance: Interview Preparation
  3. Paper 1 | General Hindi: भाषा, लिपि, ध्वनि, वर्ण, अक्षर, स्वर, व्यंजन, मात्रा और संयुक्ताक्षर, वर्तनी, वर्ण-विन्यास, अनुस्वार, अनुनासिक, चंद्रबिंदु और ‘र’ के रूप, शब्द, पद और शब्द-भेद, संज्ञा और सर्वनाम, विशेषण और क्रिया, लिंग, वचन, पुरुष और कारक, काल, वाच्य, वाक्य और वाक्य-भेद, वर्णमाला, समास, संधि, विलोम शब्द, पर्यायवाची शब्द, सामान्य अशुद्धियाँ, अनेक शब्दों के लिए एक शब्द, मुहावरे और लोकोक्तियाँ, अपठित गद्यांश और अपठित पद्यांश, Multi-Topic Content (Cross-Concept Material)
  4. Paper 2 | General Studies: State Wise GK, Polity, Geography, History, GK- Current Affairs
  5. Paper 1 | Programming Language: Language Design, C Fundamentals, Control Flow, Functions, Arrays & Pointers, Storage Classes, Structures & Enums, DMA, Macros, Scoping & File Handling, OOPS with C++
  6. Paper 1 | Database Management Systems: Basics of DBMS, ER Diagram, Relational Model & Functional Dependencies, Keys & Integrity Constraints, Normalization (1NF - BCNF), Decomposition Properties & 4NF, File Organization & Indexing, Relational Algebra, SQL, Relational Calculus, Transaction Management, Concurrency Control, ORDBMS, NoSQL
  7. Paper 1 | Cyber Security: Society, Law & Ethics, Cyber Threats and Malware Attacks, Role of Internet and Web Services, Security in Mobile and Wireless Computing, Electronic Data Interchange and E-Commerce, Physical Security and Cryptography Basics, Intrusion Detection Systems (IDS), Cyber Safety and Security, Ethical Hacking
  8. Paper 1 | Computer Organization and Architecture: Basics of COA, Programming the Basic Computer, Cache Memory Organization, Input Output Organisation, Instr Formats & Modes, Register Transfer and Microoperations, Control Unit Design
  9. Paper 1 | Computer Networks: Introduction to CN, Data Communication, DLL: Access Control, DLL: Flow Control, DLL: Error Control, DLL: Framing, Data Link Layer - Ethernet, Net Layer: IPv4 & Proto, Net Layer: IP Addressing, Net Layer:Routing Protocol, Transport Layer Services, TL: Congestion & UDP, Application Layer, Hardware basics, Network Security
  10. Paper 1 | Design and Analysis of Algorithms: Algorithm Analysis, Time Complexity Analysis, Sorting Algorithms, Greedy Algorithms, Dynamic Programming, Minimum Spanning Trees, Shortest Path Algos, Advanced Algorithms
  11. Paper 1 | Data Structures: Introduction to DS, Array, Linked List, Stack, Queue, Tree, Graphs, Hashing
  12. Paper 1 | Discrete Structures and Theory of Logic: Permutation and Combination, Set Theory, Relations, Functions, Propositional and Predicate Logic, Graph Theory, Group Theory
  13. Paper 1 | Software Project Management: Software Project Management
  14. Paper 2 | Operating Systems: Introduction to OS, Process Management, CPU Scheduling, Process Synchronization, Threads & Process Creation, Deadlock, Memory Management, Virtual Memory, Disc Scheduling, File Management, Unix OS, Linux OS, Security
  15. Paper 2 | Compiler Design: Intro to Compilers, Lexical Analysis, Grammar & CFG, Syntax Analysis: Top-Down, Syntax Analysis: Bottom-Up, Semantic Analysis & SDT, Intermediate Code Gen, Code Optimization, Run Time Environment, Introduction to TOC, Deterministic FA (DFA), Non-Deterministic FA, Regular Expressions, Pushdown Automata & CFG, Complexity Theory
  16. Paper 2 | Artificial Intelligence & High Performance Computing: Approaches to AI, Search Algorithms, Game Playing, Knowledge Representation, Planning, Multi Agent Systems, Natural Language Processing, Emerging Tech Trends
  17. Paper 2 | Image Processing: Digital Image Fundamentals, Image Enhancement, Image Restoration, Color Image Processing, Image Compression
  18. Paper 2 | Software Engineering: Fundamentals of Software Engineering, Software Requirements and Quality Assurance, Software Design, Estimation and Metrics, Software Testing, Software Maintenance and Configuration Management
  19. Paper 2 | Computer Graphics: Basics of Computer Graphics, 2-D Geometrical Transforms and Viewing, 3-D Object Representation, Geometric Transformations and Viewing
  20. Paper 2 | Web Technologies: Website, Browser & Services, Internet Fundamentals, Web Design & Development, Protocols & Services, Web Publishing & Hosting, Server Side & Security, Emerging Technologies, HTML Basics, JavaScript-Basics, Java
  21. Paper 2 | Soft Computing: Fuzzy Sets, Artificial Neural Networks, Genetic Algorithms
  22. Paper 2 | Distributed System: Distributed Systems
  23. UPPSC Live Class Recordings: UPPSC Polytechnic Lecturer 2025 (CS)
  24. Previous Year Papers:
  25. Mock Test:
AI summary & chapters

AI Summary

An AI-generated summary of this video lecture.

This lecture introduces the architecture of a Bottom-Up LR Parser, detailing its three main components: input buffer, parse stack, and parse table. It progresses to explain the construction of the LR parser table, covering augmented grammars, LR(0) items, canonical collections, and the closure and GOTO functions used to generate the parser states. The instructor uses diagrams and text slides to illustrate the flow of data and the logic behind parsing decisions, providing a comprehensive overview of the theoretical underpinnings of LR parsing.

Chapters

  1. 0:00 – 2:00 00:00-02:00

    The video begins with a slide titled 'Model of an LR Parser', listing three components: i/p buffer, Parse stack, and Parse table. The instructor highlights the input buffer cells containing symbols $a_1, a_2, \dots, a_n, \$$ and the stack containing states $S_m, X_m, \dots, S_0$. He explains the central 'LR Parsing Program (driver)' box, which uses the parse table to decide operations. The table is split into 'action' and 'goto' parts, governing 'shift', 'reduce', 'accept', and 'error' operations based on the current state and input symbol. Arrows indicate the flow of information between the input, stack, and the driver program. The 'action' table lists 'shift', 'reduce', 'accept', 'error', while the 'goto' table is labeled 'DFA'.

  2. 2:00 – 5:00 02:00-05:00

    The lecture transitions to text slides defining these components. The input buffer is described as cells holding one input symbol each. The stack holds grammar symbols pushed or popped via shift and reduce operations. The parse table is constructed using terminals, non-terminals, and LR(0) items, consisting of an 'Action' part for terminals and a 'Goto' part for non-terminals. A table structure is shown with columns for terminals ($t_1, t_2$) and non-terminals. The instructor then presents a grammar $A ightarrow aA / b$ and draws its state diagram with states $I_0$ through $I_4$, along with the corresponding parse table. He concludes this section by defining LR(K), where L stands for left-to-right scanning, R for reverse of right-most derivation, and K for the Look-Ahead symbol. The slide 'Operation in shift/reduced passer' lists 'shift', 'reduced', 'accept', 'error'. The table shows 'Action' for terminals and 'Goto' for non-terminals.

  3. 5:00 – 6:47 05:00-06:47

    The final section details the 'Procedure for the construction of LR Parser table'. Step 1 is obtaining the augmented grammar by adding a new start symbol $S' ightarrow S$. Step 2 involves creating the canonical collection of LR items. Step 3 is drawing the DFA and preparing the table. The instructor defines an LR(0) item as a production with a dot anywhere on the RHS, such as $A ightarrow .abc$. He explains the 'Closure' function: if $A ightarrow \alpha.eta B$ is in the closure, add $B ightarrow .\delta$ for all productions $B ightarrow \delta$. He also explains the 'GOTO' function, where $GOTO(I, X)$ moves the dot past symbol X to form a new set of items, which is then closed. The slide 'Function used to generate LR(0) item's' shows the specific formulas for these operations, including $GOTO(A ightarrow \alpha.Xeta, X) = A ightarrow \alpha X . eta$. The instructor draws diagrams to illustrate the closure process, showing how new items are added to the set. He emphasizes that the GOTO function is used to transition between states in the DFA based on the input symbol.

The lecture systematically builds the theoretical foundation for LR parsing, moving from the high-level model of the parser to the specific algorithms required to construct the parsing table, emphasizing the roles of augmented grammars and item sets. It connects the abstract definitions of LR items to the concrete steps of building the parser table.

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