###
# sample calculator
#

input      ::= ws expr ws eoi;

expr       ::= ws powterm expr_arg1 [{ws '^' ws powterm expr_arg2}];
powterm    ::= ws factor powterm_arg1 [{ws ('*' powterm_mul | '/' powterm_div) ws factor powterm_arg2}];
factor     ::= ws term factor_arg1 [{ws ('+' factor_add | '-' factor_sub) ws term factor_arg2 }];
term       ::= '(' ws expr ws ')' term_paren | '-' ws expr term_minus | number term_number;

number     ::= number_start {dgt} ['.' {dgt}] [('e'|'E') ['-'] {dgt}] number_end;
dgt        ::= '0'|'1'|'2'|'3'|'4'|'5'|'6'|'7'|'8'|'9';
ws         ::= [{' '|'\t'|'\n'|'\r'}];

%%

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <math.h>

extern double expr_value;

int debug = 1;
   
/* program entry */
int main(int argc,char* argv[])
{
	int i;
	
	if (argc == 1) {
		printf("Usage: %s EXPRESSION...\n",argv[0]);
		return 1;
	}

	for (i = 1; i < argc; i++)
	{
		char not_used[10];
		int retval;
		
		retval = __BNF_str_io_parser(argv[i],not_used, input);

		if (retval == 0)
			printf("%s = %f\n",argv[i],expr_value);
		else
			printf("%s = syntax error\n",argv[i]);
	}
	
	return 0;
}

/*
 * parser functions
 */

/* number */
char* number_start_pos;
double number_value;
number_start()
{
	number_start_pos = __BNF_input;

	return 0;
}
number_end()
{
	char tmp[64];
	
	strncpy(tmp, number_start_pos, __BNF_input - number_start_pos);
	tmp[__BNF_input - number_start_pos] = '\0';
	number_value = atof(tmp);
	
	if (debug) printf("Got number `%s' = %f\n",tmp,number_value);

	return 0;
}

/* term */
double term_value;
term_paren()
{
	term_value = expr_value;

	if (debug) printf("term: got paren: term_value = %f\n",term_value);
	return 0;
}
term_minus()
{
	term_value = -expr_value;

	if (debug) printf("term: got unary minus: term_value = %f\n",term_value);
	return 0;
}
term_number()
{
	term_value = number_value;
	
	if (debug) printf("term: got number: term_value = %f\n",term_value);
	return 0;
}

/* factor */
int factor_opmode;  /* 1 = add, 2 = sub */
double factor_value;
factor_arg1()
{
	factor_value = term_value;

	if (debug) printf("factor: got first num: factor_value = %f\n",factor_value);
	return 0;
}
factor_add()
{
	factor_opmode=1;
	return 0;
}
factor_sub()
{
	factor_opmode=2;
	return 0;
}
factor_arg2()
{
	switch(factor_opmode) {
		case 1: factor_value += term_value; break;
		case 2: factor_value -= term_value; break;
	}

	if (debug) printf("factor: got second num: factor_value = %f\n",factor_value);
	return 0;
}

/* powterm */
int powterm_opmode; /* 1 = mul, 2 = div */
double powterm_value;
powterm_arg1()
{
	powterm_value = factor_value;

	if (debug) printf("powterm: got first num: powterm_value = %f\n",powterm_value);
	return 0;
}
powterm_mul()
{
	powterm_opmode = 1;
	return 0;
}
powterm_div()
{
	powterm_opmode = 2;
	return 0;
}
powterm_arg2()
{
	switch(powterm_opmode) {
		case 1: powterm_value *= factor_value; break;
		case 2: powterm_value /= factor_value; break;
	}

	if (debug) printf("powterm: got second num: powterm_value = %f\n",powterm_value);
	return 0;
}

/* expr */
double expr_value = -1;
expr_arg1()
{
	expr_value = powterm_value;

	if (debug) printf("expr: got first num: expr_value = %f\n",expr_value);
	return 0;
}
expr_arg2()
{
//	expr_value = pow(expr_value, powterm_value);

	if (debug) printf("expr: got second num: expr_value = %f\n",expr_value);
	return 0;
}