# Rules providing basic arithmetic operations

HAIKU_PAD_9 = 0 1 2 3 4 5 6 7 8 ;

# a > b <==> $(HAIKU_DIGIT_GREATER_$(a)[1$(b)])
HAIKU_DIGIT_GREATER_0 = $(HAIKU_PAD_9) ;
HAIKU_DIGIT_GREATER_1 = $(HAIKU_PAD_9) 1 ;
HAIKU_DIGIT_GREATER_2 = $(HAIKU_PAD_9) 1 1 ;
HAIKU_DIGIT_GREATER_3 = $(HAIKU_PAD_9) 1 1 1 ;
HAIKU_DIGIT_GREATER_4 = $(HAIKU_PAD_9) 1 1 1 1 ;
HAIKU_DIGIT_GREATER_5 = $(HAIKU_PAD_9) 1 1 1 1 1 ;
HAIKU_DIGIT_GREATER_6 = $(HAIKU_PAD_9) 1 1 1 1 1 1 ;
HAIKU_DIGIT_GREATER_7 = $(HAIKU_PAD_9) 1 1 1 1 1 1 1 ;
HAIKU_DIGIT_GREATER_8 = $(HAIKU_PAD_9) 1 1 1 1 1 1 1 1 ;
HAIKU_DIGIT_GREATER_9 = $(HAIKU_PAD_9) 1 1 1 1 1 1 1 1 1 ;

# a + b == $(HAIKU_DIGIT_ADD_$(a)[1$(b)]) (carry ignored)
HAIKU_DIGIT_ADD_0 = $(HAIKU_PAD_9) 0 1 2 3 4 5 6 7 8 9 ;
HAIKU_DIGIT_ADD_1 = $(HAIKU_PAD_9) 1 2 3 4 5 6 7 8 9 0 ;
HAIKU_DIGIT_ADD_2 = $(HAIKU_PAD_9) 2 3 4 5 6 7 8 9 0 1 ;
HAIKU_DIGIT_ADD_3 = $(HAIKU_PAD_9) 3 4 5 6 7 8 9 0 1 2 ;
HAIKU_DIGIT_ADD_4 = $(HAIKU_PAD_9) 4 5 6 7 8 9 0 1 2 3 ;
HAIKU_DIGIT_ADD_5 = $(HAIKU_PAD_9) 5 6 7 8 9 0 1 2 3 4 ;
HAIKU_DIGIT_ADD_6 = $(HAIKU_PAD_9) 6 7 8 9 0 1 2 3 4 5 ;
HAIKU_DIGIT_ADD_7 = $(HAIKU_PAD_9) 7 8 9 0 1 2 3 4 5 6 ;
HAIKU_DIGIT_ADD_8 = $(HAIKU_PAD_9) 8 9 0 1 2 3 4 5 6 7 ;
HAIKU_DIGIT_ADD_9 = $(HAIKU_PAD_9) 9 0 1 2 3 4 5 6 7 8 ;

# pragma mark - Number Operations

rule AddNumAbs a : b
{
	# AddNum <a> : <b> ;

	local result ;
	local carry ;
	while $(a) || $(b) || $(carry) {
		# chop off the first digit
		local da = $(a[1]:E=0) ;
		local db = $(b[1]:E=0) ;
		a = $(a[2-]) ;
		b = $(b[2-]) ;

		# add carry to the first digit
		if $(carry) {
			local daa = $(HAIKU_DIGIT_ADD_1[1$(da)]) ;
			carry = $(HAIKU_DIGIT_GREATER_$(da)[1$(daa)]) ;
			da = $(daa) ;
		}

		# add digits
		local dr = $(HAIKU_DIGIT_ADD_$(da)[1$(db)]) ;
		if $(HAIKU_DIGIT_GREATER_$(da)[1$(dr)]) {
			carry = 1 ;
		}

		result += $(dr) ;
	}

	return $(result) ;
}