Aim: Write a yacc program that accepts a regular expression as input and produce its parse tree as output. Description: Yacc- Yet another C Compiler defines what it is all by itself.
Algorithm: Start Accept an expression from the user. Check for the structure that satisfies the conditions of a regular expression. Print the parsed tree as output as when the conditions are satisfied. Make Files Executable. Execute the shell script. Passing parameters to a Shell script. In above case 0th parameter value considered will be script name.
Accessing parameters in a Shell script. Shell Positional Variable. Sh filename. A Compiler is a program takes a program written in a source language and translates it into an equivalent program in a target language. Source Program Compiler Target Program. Generally written in a.
High level language. Error Messages. Major Parts of Compilers :. Phases of a Compiler. Intermediate Code Generation. But the level of intermediate codes is close to the level of machine codes. MULT id2, id3,temp1. ADD temp1, 1,temp2. MOV temp2,,id1. Code Generator. MOVE id2,R1. MULT id3,R1. ADD 1,R1. MOVE R1,id1. LEX Programs.
Also eliminate them and copy that file into another file. Print them separately. A start B. PART B. Unix Programming:.
Thus if the script generated by this script ids executed, it would recreate the original file. The child process prints its own pid and id of its parent and then exists.
The parent process waits for its child process and then exists. Write a yacc program that accepts a regular expression as input and produce its parse tree. Viva Questions. System Software. What is a System? Systems have interconnectivity; the various parts of a system have functional as well as structural relationships to each other.
What is System software? System software is computer software designed to operate the computer hardware and to provide a platform for running application software. Difference between System software and application software. What is an Assembler? Assembler for an assembly language, a computer program to translate between lower-level representations of computer programs.
An assembler converts basic computer instructions into a pattern of bits which can be easily understood by the computer and the processor can use it to perform its basic operations. What is an editor? Text editors are often provided with operating systems or software development packages, and can be used to change configuration files and language source. What is a linker? Linker computing , a computer program that takes one or more objects generated by a compiler and combines them into a single executable program.
What is a compiler? A compiler is a computer program or set of programs that transforms source code written in a programming language the source language into another computer language the target language , often having a binary form known as object code.
The most common reason for wanting to transform source code is to create an executable program. What is a Loader? A loader is the part of an operating system that is responsible for loading programs.
Loading a program involves reading the contents of executable file , the file containing the program text, into memory, and then carrying out other required preparatory tasks to prepare the executable for running.
What is a Debugger? A debugger or debugging tool is a program that is used to test and debug other programs the "target" program. What is a Interpreter? A n interpreter normally means a computer program that executes, i. An interpreter may be a program that either executes the source code directly and translates source code into some efficient intermediate representation code and immediately executes. Lex and Yacc. Explain lex and yacc tools Lex: - scanner that can identify those tokens.
Yacc: - parser. Give the structure of the lex program Rules section- pattern and action separated by white space. User subroutines section-concsit of any legal code.
Explain yytext:- contains the text that matched the pattern. The yacc produced by parser is called yyparse. Explain the structure of a yacc program? Defn section- declarations of the tokens used in the grammar. The rules section-pattern action. Users subroutines section. Yyleng-contains the length of the string our lexer recognizes. Define action? The C code associated with a lex pattern or a yacc rule. When the pattern or rule matches an input sequence, the action code is executed.
Define Pattern? In a lex lexer, a regular expression that the lexer matches against the input. What is an Alphabet? A set of distinct symbols. American Standard Code for Information Interchange, a collection of symbols representing the common symbols found in the American alphabet: lower and upper case letters, digits and punctuation, plus additional characters for formatting and control of data communication links. What is an Ambiguity? An Ambiguous grammar is one with more than one rule or set of rules that match the same input.
Next, the output of that phase goes to the syntax analysis. It takes the tokens of the lexical analysis and produces a parse tree as the output. Overall, the lexical analyzer performs the lexical analysis while syntax analyzer performs syntax analysis. Lex is a lexical analyzer whereas Yacc is a parser. Both work together. For example, Lex takes the string input to create tokens, and Yacc uses those tokenized input.
What is Lex -Definition, Functionality 2. What is Yacc — Definition, Functionality 3. Difference Between Lex and Yacc -Comparison of key differences. Lex is a computer program that generates lexical analyzers.
Mike Lex and Eric Schmidt are the original developers of Lex. It is a standard lexical analyzer generator on various UNIX systems. Generally, Lex is used with Yacc parse generator.
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