%{

/* compile:	leg -o calc.c calc.leg
 *		cc -o calc calc.c
 *
 * run:		( echo a=2*3; echo b=3+4; echo c=a*b ) | ./calc
 */

#define SYMBOL_PAYLOAD				\
	oop     value;				\
	int     defined

#define SYMBOL_INITIALISE(S)			\
	S.value = null;				\
	S.defined = false

#include "object.c"

// this should stay out of object.c because it manipulates Symbol members defined in this file

oop update_symbol_value(oop symbol, oop integer)
{
	//_checkType(symbol, Symbol);
	// For now it will fail with assigning to null
	// because for now we can write "a=2 b=a" because everything is passed by value
	//_checkType(integer, Integer);
	set(symbol, Symbol,value, integer); // checktyype is implicit, and it's ok for symbols to store any object value?
	return symbol;
}

#define YYSTYPE oop

YYSTYPE yylval;

%}

start	=	e:exp					{ yylval = e }

exp	=	- (a:assign				{ $$ = a }
		| s:sum 				{ $$ = s }
		)

assign	=	l:IDENT EQUAL n:sum			{ $$ = update_symbol_value(l, n) }

sum	=	l:prod ### removed PLUS* from beginning and made + a prefix operator just like - instead
			( PLUS+ r:prod			{ get(l, Integer, value) += get(r, Integer, value) }
			| MINUS r:prod			{ get(l, Integer, value) -= get(r, Integer, value) }
			)*				{ $$ = l }

prod	=	l:neg
			( MULTI		r:neg		{ get(l, Integer, value) *= get(r, Integer, value) }
			| DIVIDE	r:neg		{ get(l, Integer, value) /= get(r, Integer, value) }
			| MODULO	r:neg		{ get(l, Integer, value) %= get(r, Integer, value) }
			)*				{ $$ = l }

neg	=	MINUS n:neg				{ set(n, Integer, value, -get(n, Integer, value));  $$ = n }
	|       PLUS  n:neg				{ $$ = n } ### moved from sum
	|	n:value					{ $$ = n }

value	=	n:NUMBER				{ $$ = n }
	|	NULL					{ $$ = null; /* For now it doesn't work because of _checktype in update_symbol_value() */ }
	|	l:IDENT					{ $$ = get(l, Symbol, value); // Will result in an assertion failed if ident is undefined }

-	=	[ \t\n\r]* ### added newline and carriage return to allow multi-line `programs'
NUMBER	=	< [0-9]+ >	-			{ $$ = makeInteger(atoi(yytext)) }
IDENT	=	< [a-zA-Z][a-zA-Z0-9_]* >	-	{ $$ = intern(yytext) }
PLUS	=	'+'			-
MINUS	=	'-'			-
MULTI	=	'*'			-
DIVIDE	=	'/'			-
MODULO	=	'%'			-
EQUAL	=	'='			-
NULL	=	'null'		-

%%

int main(int argc, char **argv)
{
	while (yyparse()) {
		println(yylval);
	}

	return 0;
}