// Program name as “lexicalfile.l”
%{
#include<stdio.h>
%}
delim [\t]
ws {delim}+
letter [A-Za-z]
digit [0-9]
id {letter}({letter}|{digit})*
num {digit}+(\.{digit}+)?(E[+|-]?{digit}+)?
%%
ws {printf("no action");}
if|else|then {printf("%s is a keyword",yytext);} // TYPE 32 KEYWORDS
{id} {printf("%s is a identifier",yytext);}
{num} {printf(" it is a number");}
"<" {printf("it is a relational operator less than");}
"<=" {printf("it is a relational operator less than or equal");}
">" {printf("it is a relational operator greater than");}
">=" {printf("it is a relational operator greater than");}
"==" {printf("it is a relational operator equal");}
"<>" {printf("it is a relational operator not equal");}
%%
main()
{
yylex();
}
OUTPUT
lexlexicalfile.l
cc lex.yy.c -ll
if
if is a keyword
number
number is a identifier
254
It is a number
<>
it is a relational operator not equal
^Z
