What does a parser do in a compiler?

A parser is a compiler or interpreter component that breaks data into smaller elements for easy translation into another language. A parser takes input in the form of a sequence of tokens, interactive commands, or program instructions and breaks them up into parts that can be used by other components in programming.

What is yacc tool in compiler design?

Yacc (yet another compiler compiler) is a grammar parser and parser generator. That is, it is a program that reads a grammar specification and generates code that is able to organize input tokens in a syntactic tree in accordance with the grammar.

Which parsing technique is more efficient *?

The LR parser is a non-recursive, shift-reduce, bottom-up parser. It uses a wide class of context-free grammar which makes it the most efficient syntax analysis technique.

Why is parsing used?

Parsing is used to derive a string using the production rules of a grammar. It is used to check the acceptability of a string. Compiler is used to check whether or not a string is syntactically correct. A parser takes the inputs and builds a parse tree.

What does $$ mean in YACC?

$$ stands for the result of the current rule. $1 and $3 stand for the results of the first and third components respectively. So in this case, $1 would hold the value of the left num token and $3 of the right one.

Why is YACC used?

YACC provides a tool to produce a parser for a given grammar. YACC is a program designed to compile a LALR (1) grammar. It is used to produce the source code of the syntactic analyzer of the language produced by LALR (1) grammar. The input of YACC is the rule or grammar and the output is a C program.

What are the topics in the compiler design book?

Topics covered are: Overview of compilers, Scanners and lexical analysis, Parsing, Static semantics, type checking, and symbol tables, Runtime organization and code shape, Code generation – instruction selection and scheduling, Register allocation, Program analysis, optimization, and program transformations.

Why is the compiler book called the Dragon Book?

It is affectionately known as the Dragon Book to generations of computer scientists as its cover depicts a knight and a dragon in battle, a metaphor for conquering complexity. This name can also refer to Aho and Ullman’s older Principles of Compiler Design .

How is the predictive parser used in the compiler?

To accomplish its tasks, the predictive parser uses a look-ahead pointer, which points to the next input symbols. To make the parser back-tracking free, the predictive parser puts some constraints on the grammar and accepts only a class of grammar known as LL (k) grammar.

What are the topics in the one pass compiler?

This lecture note explains the following topics: Introduction to Compiling, A Simple One-Pass Compiler, Lexical Analysis, Syntax Analysis, Syntax-Directed Translation, Type Checking, Run-Time Environments, Intermediate Code Generation, Code generation, Code Optimization.