Lex Program to remove comments from C program
Last Updated :
11 Jul, 2022
Lex is a computer program that generates lexical analyzers. Lex reads an input stream specifying the lexical analyzer and outputs source code implementing the lexer in the C programming language.
The commands for executing the lex program are:
lex abc.l (abc is the file name)
cc lex.yy.c -efl
./a.out
Let’s see LEX program to accept string starting with vowel.
Examples:
Input :
//testing
#include
int main()
{
/* multiline comment
continue....
*/
return 0;
}
Output :
#include
int main()
{
return 0;
}
Below is the implementation:
/
and save it in a file
/*Definition Section*/
/*Starting character sequence for multiline comment*/
start \/\*
/*Ending character sequence for multiline comment*/
end \*\/
/*Rule Section*/
/*Regular expression for single line comment*/
\/\/(.*) ;
/*Regular expression for multi line comment*/
{start}.*{ end } ;
/*Driver function */
int main(int k,char **argcv)
{
yyin=fopen(argcv[1], "r" );
yyout=fopen( "out.c" , "w" );
/*call the yylex function .*/
yylex();
return 0;
}
|
Output:
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