%{

/* define constants for C program here */
#include <stdlib.h>
#include <string.h>

enum {
	LT, LE,
	EQ, NE,
	GT, GE
};

enum {
	IF = 1,
	THEN, ELSE,
	RELOP, ID, NUM
};

struct token {
	int type;
	double value;
} yylval;

/* declare symbol table management functions. */
void set_default_type();
int init_symtbl();
int install_id();
int gettoken();
char* get_id();

%}

/* regular definitions */
delim	[ \t\n]
ws	{delim}+
letter	[A-Za-z]
digit	[0-9]
id	{letter}({letter}|{digit})*
number	{digit}+(\.{digit}+)?(E[+\-]?{digit}+)?

%%

{ws}		{/* no action and no return */}

{id}		{yylval.type = gettoken(yytext); yylval.value = install_id(yytext); return(yylval.type);}
{number}	{yylval.value = atof(yytext); return(NUM);}

"<"		{yylval.value = LT; return(RELOP);}
"<="		{yylval.value = LE; return(RELOP);}
"="		{yylval.value = EQ; return(RELOP);}
"<>"		{yylval.value = NE; return(RELOP);}
">"		{yylval.value = GT; return(RELOP);}
">="		{yylval.value = GE; return(RELOP);}

%%
#include "symtable.c"

main()
{
	int token;

	set_default_type(ID);
	init_symtbl(IF, "if");
	init_symtbl(THEN, "then");
	init_symtbl(ELSE, "else");
	
	while(token=yylex()) {
		printf("TOKEN ");
		switch(token) {
		case ID:
			printf("ID, lexeme = %s\n", get_id((int)yylval.value));
			break;
		case NUM:
			printf("NUM, value = %f\n", yylval.value);
			break;
		case RELOP:
			printf("RELOP, symbol = %d\n", (int)yylval.value);
			break;
		default:
			printf("KEYWORD, type=%d\n", yylval.type);
		}
	}
}