Lex Program to remove comments from C program
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:
/% Lex Program to remove comments from C program 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:
