acme/src/alu.c

// ACME - a crossassembler for producing 6502/65c02/65816 code.
// Copyright (C) 1998-2014 Marco Baye
// Have a look at "acme.c" for further info
//
// Arithmetic/logic unit
// 11 Oct 2006	Improved float reading in parse_decimal_value()
// 24 Nov 2007	Now accepts floats starting with decimal point
// 31 Jul 2009	Changed ASR again, just to be on the safe side.
// 14 Jan 2014	Changed associativity of "power-of" operator,
//		so a^b^c now means a^(b^c).
//  7 May 2014	C-style "==" operators are now recognized (but
//		give a warning).
// 31 May 2014	Added "0b" binary number prefix as alternative to "%".
#include <stdlib.h>
#include <math.h>	// only for fp support
#include "platform.h"
#include "alu.h"
#include "dynabuf.h"
#include "encoding.h"
#include "global.h"
#include "input.h"
#include "label.h"
#include "output.h"
#include "section.h"
#include "tree.h"


// constants

#define FUNCTION_DYNABUF_INITIALSIZE	8	// enough for "arctan"
#define HALF_INITIAL_STACK_SIZE	8
static const char	exception_div_by_zero[]	= "Division by zero.";
static const char	exception_no_value[]	= "No value given.";
static const char	exception_paren_open[]	= "Too many '('.";
static const char	exception_undefined[]	= "Value not defined.";
#define s_or	(s_eor + 1)	// Yes, I know I'm sick
#define s_xor	(s_scrxor + 3)	// Yes, I know I'm sick
static const char	s_arcsin[]	= "arcsin";
#define s_sin	(s_arcsin + 3)	// Yes, I know I'm sick
static const char	s_arccos[]	= "arccos";
#define s_cos	(s_arccos + 3)	// Yes, I know I'm sick
static const char	s_arctan[]	= "arctan";
#define s_tan	(s_arctan + 3)	// Yes, I know I'm sick

// operator handles (FIXME - use function pointers instead? or too slow?)
enum operator_handle {
//	special values (pseudo operators)
	OPHANDLE_END,		//		"reached end of expression"
	OPHANDLE_RETURN,	//		"return value to caller"
//	functions
	OPHANDLE_INT,		//	int(v)
	OPHANDLE_FLOAT,		//	float(v)
	OPHANDLE_SIN,		//	sin(v)
	OPHANDLE_COS,		//	cos(v)
	OPHANDLE_TAN,		//	tan(v)
	OPHANDLE_ARCSIN,	//	arcsin(v)
	OPHANDLE_ARCCOS,	//	arccos(v)
	OPHANDLE_ARCTAN,	//	arctan(v)
//	monadic operators
	OPHANDLE_OPENING,	//	(v	'(', starts subexpression
	OPHANDLE_NOT,		//	!v	NOT v	bit-wise NOT
	OPHANDLE_NEGATE,	//	-v		Negate
	OPHANDLE_LOWBYTEOF,	//	<v		Lowbyte of
	OPHANDLE_HIGHBYTEOF,	//	>v		Highbyte of
	OPHANDLE_BANKBYTEOF,	//	^v		Bankbyte of
//	dyadic operators
	OPHANDLE_CLOSING,	//	v)	')', ends subexpression
	OPHANDLE_POWEROF,	//	v^w
	OPHANDLE_MULTIPLY,	//	v*w
	OPHANDLE_DIVIDE,	//	v/w		(Integer) Division
	OPHANDLE_INTDIV,	//	v/w	v DIV w	Integer Division
	OPHANDLE_MODULO,	//	v%w	v MOD w	Remainder
	OPHANDLE_SL,		//	v<<w	v ASL w	v LSL w	Shift left
	OPHANDLE_ASR,		//	v>>w	v ASR w	Arithmetic shift right
	OPHANDLE_LSR,		//	v>>>w	v LSR w	Logical shift right
	OPHANDLE_ADD,		//	v+w
	OPHANDLE_SUBTRACT,	//	v-w
	OPHANDLE_EQUALS,	//	v=w
	OPHANDLE_LE,		//	v<=w
	OPHANDLE_LESSTHAN,	//	v< w
	OPHANDLE_GE,		//	v>=w
	OPHANDLE_GREATERTHAN,	//	v> w
	OPHANDLE_NOTEQUAL,	//	v!=w	v<>w	v><w
	OPHANDLE_AND,		//	v&w		v AND w
	OPHANDLE_OR,		//	v|w		v OR w
	OPHANDLE_EOR,		//	v EOR w		v XOR w		(FIXME:remove)
	OPHANDLE_XOR,		//	v XOR w
};
struct operator {
	enum operator_handle	handle;
	char			priority_and_associativity;
};
#define IS_RIGHT_ASSOCIATIVE(p)	((p) & 1)	// lsb of priority value signals right-associtivity

// operator structs (only hold handle and priority/associativity value)
static struct operator ops_end		= {OPHANDLE_END,	0};	// special
static struct operator ops_return	= {OPHANDLE_RETURN,	2};	// special
static struct operator ops_closing	= {OPHANDLE_CLOSING,	4};	// dyadic
static struct operator ops_opening	= {OPHANDLE_OPENING,	6};	// monadic
static struct operator ops_or		= {OPHANDLE_OR,		8};	// dyadic
static struct operator ops_eor		= {OPHANDLE_EOR,	10};	//	(FIXME:remove)
static struct operator ops_xor		= {OPHANDLE_XOR,	10};	// dyadic
static struct operator ops_and		= {OPHANDLE_AND,	12};	// dyadic
static struct operator ops_equals	= {OPHANDLE_EQUALS,	14};	// dyadic
static struct operator ops_notequal	= {OPHANDLE_NOTEQUAL,	16};	// dyadic
	// same priority for all comparison operators (left-associative)
static struct operator ops_le		= {OPHANDLE_LE,		18};	// dyadic
static struct operator ops_lessthan	= {OPHANDLE_LESSTHAN,	18};	// dyadic
static struct operator ops_ge		= {OPHANDLE_GE,		18};	// dyadic
static struct operator ops_greaterthan	= {OPHANDLE_GREATERTHAN,18};	// dyadic
	// same priority for all byte extraction operators
static struct operator ops_lowbyteof	= {OPHANDLE_LOWBYTEOF,	20};	// monadic
static struct operator ops_highbyteof	= {OPHANDLE_HIGHBYTEOF,	20};	// monadic
static struct operator ops_bankbyteof	= {OPHANDLE_BANKBYTEOF,	20};	// monadic
	// same priority for all shift operators (left-associative, though they could be argued to be made right-associative :))
static struct operator ops_sl		= {OPHANDLE_SL,		22};	// dyadic
static struct operator ops_asr		= {OPHANDLE_ASR,	22};	// dyadic
static struct operator ops_lsr		= {OPHANDLE_LSR,	22};	// dyadic
	// same priority for "+" and "-" (left-associative)
static struct operator ops_add		= {OPHANDLE_ADD,	24};	// dyadic
static struct operator ops_subtract	= {OPHANDLE_SUBTRACT,	24};	// dyadic
	// same priority for "*", "/" and "%" (left-associative)
static struct operator ops_multiply	= {OPHANDLE_MULTIPLY,	26};	// dyadic
static struct operator ops_divide	= {OPHANDLE_DIVIDE,	26};	// dyadic
static struct operator ops_intdiv	= {OPHANDLE_INTDIV,	26};	// dyadic
static struct operator ops_modulo	= {OPHANDLE_MODULO,	26};	// dyadic
	// highest "real" priorities
static struct operator ops_negate	= {OPHANDLE_NEGATE,	28};	// monadic
static struct operator ops_powerof	= {OPHANDLE_POWEROF,	29};	// dyadic, right-associative
static struct operator ops_not		= {OPHANDLE_NOT,	30};	// monadic
	// function calls act as if they were monadic operators
static struct operator ops_int		= {OPHANDLE_INT,	32};	// function
static struct operator ops_float	= {OPHANDLE_FLOAT,	32};	// function
static struct operator ops_sin		= {OPHANDLE_SIN,	32};	// function
static struct operator ops_cos		= {OPHANDLE_COS,	32};	// function
static struct operator ops_tan		= {OPHANDLE_TAN,	32};	// function
static struct operator ops_arcsin	= {OPHANDLE_ARCSIN,	32};	// function
static struct operator ops_arccos	= {OPHANDLE_ARCCOS,	32};	// function
static struct operator ops_arctan	= {OPHANDLE_ARCTAN,	32};	// function


// variables
static struct dynabuf	*function_dyna_buf;	// dynamic buffer for fn names
static struct operator	**operator_stack	= NULL;
static int		operator_stk_size	= HALF_INITIAL_STACK_SIZE;
static int		operator_sp;		// operator stack pointer
static struct result_t	*operand_stack		= NULL;	// flags and value
static int		operand_stk_size	= HALF_INITIAL_STACK_SIZE;
static int		operand_sp;		// value stack pointer
static int		indirect_flag;	// Flag for indirect addressing
					// (indicated by useless parentheses)
					// Contains either 0 or MVALUE_INDIRECT
enum alu_state {
	STATE_EXPECT_OPERAND_OR_MONADIC_OPERATOR,
	STATE_EXPECT_DYADIC_OPERATOR,
	STATE_TRY_TO_REDUCE_STACKS,
	STATE_MAX_GO_ON,	// "border value" to find the stoppers:
	STATE_ERROR,		// error has occured
	STATE_END		// standard end
};
static enum alu_state	alu_state;	// deterministic finite automaton
// predefined stuff
static struct node_t	*operator_tree	= NULL;	// tree to hold operators
static struct node_t	operator_list[]	= {
	PREDEFNODE(s_asr,	&ops_asr),
	PREDEFNODE(s_lsr,	&ops_lsr),
	PREDEFNODE(s_asl,	&ops_sl),
	PREDEFNODE("lsl",	&ops_sl),
	PREDEFNODE("div",	&ops_intdiv),
	PREDEFNODE("mod",	&ops_modulo),
	PREDEFNODE(s_and,	&ops_and),
	PREDEFNODE(s_or,	&ops_or),
	PREDEFNODE(s_eor,	&ops_eor),		// (FIXME:remove)
	PREDEFLAST(s_xor,	&ops_xor),
	//    ^^^^ this marks the last element
};
static struct node_t	*function_tree	= NULL;	// tree to hold functions
static struct node_t	function_list[]	= {
	PREDEFNODE("int",	&ops_int),
	PREDEFNODE("float",	&ops_float),
	PREDEFNODE(s_arcsin,	&ops_arcsin),
	PREDEFNODE(s_arccos,	&ops_arccos),
	PREDEFNODE(s_arctan,	&ops_arctan),
	PREDEFNODE(s_sin,	&ops_sin),
	PREDEFNODE(s_cos,	&ops_cos),
	PREDEFLAST(s_tan,	&ops_tan),
	//    ^^^^ this marks the last element
};

#define LEFT_FLAGS	(operand_stack[operand_sp-2].flags)
#define RIGHT_FLAGS	(operand_stack[operand_sp-1].flags)
#define LEFT_INTVAL	(operand_stack[operand_sp-2].val.intval)
#define RIGHT_INTVAL	(operand_stack[operand_sp-1].val.intval)
#define LEFT_FPVAL	(operand_stack[operand_sp-2].val.fpval)
#define RIGHT_FPVAL	(operand_stack[operand_sp-1].val.fpval)

#define PUSH_OPERATOR(x)	operator_stack[operator_sp++] = (x)

#define PUSH_INTOPERAND(i, f)				\
do {							\
	operand_stack[operand_sp].flags = (f);		\
	operand_stack[operand_sp++].val.intval = (i);	\
} while (0)
#define PUSH_FPOPERAND(fp, f)					\
do {								\
	operand_stack[operand_sp].flags = (f) | MVALUE_IS_FP;	\
	operand_stack[operand_sp++].val.fpval = (fp);		\
} while (0)


// handle "NeedValue" type errors: problems that may be solved by performing
// further passes. This function only counts, it will not show the errors to
// the user.
static void just_count(void)
{
	pass_undefined_count++;
}


// handle "NeedValue" type errors: problems that may be solved by performing
// further passes. This function counts these errors and shows them to the user.
static void count_and_throw(void)
{
	pass_undefined_count++;
	Throw_error(exception_undefined);
}


// function pointer for "result is undefined" type errors.
static void (*result_is_undefined)(void)	= just_count;


// activate error output for "value undefined"
void ALU_throw_errors(void)
{
	result_is_undefined = count_and_throw;
}


// enlarge operator stack
static void enlarge_operator_stack(void)
{
	operator_stk_size *= 2;
	operator_stack = realloc(operator_stack, operator_stk_size * sizeof(*operator_stack));
	if (operator_stack == NULL)
		Throw_serious_error(exception_no_memory_left);
}


// enlarge operand stack
static void enlarge_operand_stack(void)
{
	operand_stk_size *= 2;
	operand_stack = realloc(operand_stack, operand_stk_size * sizeof(*operand_stack));
	if (operand_stack == NULL)
		Throw_serious_error(exception_no_memory_left);
}


// create dynamic buffer, operator/function trees and operator/operand stacks
void ALU_init(void)
{
	function_dyna_buf = DynaBuf_create(FUNCTION_DYNABUF_INITIALSIZE);
	Tree_add_table(&operator_tree, operator_list);
	Tree_add_table(&function_tree, function_list);
	enlarge_operator_stack();
	enlarge_operand_stack();
}


// not-so-braindead algorithm for calculating "to the power of" function for
// integer operands.
// my_pow(whatever, 0) returns 1. my_pow(0, whatever_but_zero) returns 0.
static intval_t my_pow(intval_t mantissa, intval_t exponent)
{
	intval_t	result	= 1;

	while (exponent) {
		// handle exponent's lowmost bit
		if (exponent & 1)
			result *= mantissa;
		// square the mantissa, halve the exponent
		mantissa *= mantissa;
		exponent >>= 1;
	}
	return result;
}


// arithmetic shift right (works even if C compiler does not support it)
static intval_t my_asr(intval_t left, intval_t right)
{
	// if first operand is positive or zero, ASR and LSR are equivalent,
	// so just do it and return the result:
	if (left >= 0)
		return left >> right;

	// However, if the first operand is negative, the result is
	// implementation-defined: While most compilers will do ASR, some others
	// might do LSR instead, and *theoretically*, it is even possible for a
	// compiler to define silly stuff like "shifting a negative value to the
	// right will always return -1".
	// Therefore, in case of a negative operand, we'll use this quick and
	// simple workaround:
	return ~((~left) >> right);
}


// Lookup (and create, if necessary) label tree item and return its value.
// DynaBuf holds the label's name and "zone" its zone.
// This function is not allowed to change DynaBuf because that's where the
// label name is stored!
static void get_label_value(zone_t zone)
{
	struct label	*label;

	// if the label gets created now, mark it as unsure
	label = Label_find(zone, MVALUE_UNSURE);
	// in first pass, count usage
	if (pass_count == 0)
		label->usage++;
	// push operand, regardless of whether int or float
	operand_stack[operand_sp] = label->result;
	operand_stack[operand_sp++].flags |= MVALUE_EXISTS;
}


// Parse quoted character.
// The character will be converted using the current encoding.
static void parse_quoted_character(char closing_quote)
{
	intval_t	value;

	// read character to parse - make sure not at end of statement
	if (GetQuotedByte() == CHAR_EOS)
		return;

	// on empty string, complain
	if (GotByte == closing_quote) {
		Throw_error(exception_missing_string);
		Input_skip_remainder();
		return;
	}

	// parse character
	value = (intval_t) Encoding_encode_char(GotByte);
	// Read closing quote (hopefully)
	if (GetQuotedByte() == closing_quote)
		GetByte();	// if length == 1, proceed with next byte
	else
		if (GotByte) {
			// if longer than one character
			Throw_error("There's more than one character.");
			Input_skip_remainder();
		}
	PUSH_INTOPERAND(value, MVALUE_GIVEN | MVALUE_ISBYTE);
	// Now GotByte = char following closing quote (or CHAR_EOS on error)
}


// Parse binary value. Apart from '0' and '1', it also accepts the characters
// '.' and '#', this is much more readable. The current value is stored as soon
// as a character is read that is none of those given above.
static void parse_binary_value(void)	// Now GotByte = "%" or "b"
{
	intval_t	value	= 0;
	int		go_on	= TRUE,	// continue loop flag
			flags	= MVALUE_GIVEN,
			digits	= -1;	// digit counter

	do {
		digits++;
		switch (GetByte()) {
		case '0':
		case '.':
			value <<= 1;
			break;
		case '1':
		case '#':
			value = (value << 1) | 1;
			break;
		default:
			go_on = 0;
		}
	} while (go_on);
	// set force bits
	if (digits > 8) {
		if (digits > 16) {
			if (value < 65536)
				flags |= MVALUE_FORCE24;
		} else {
			if (value < 256)
				flags |= MVALUE_FORCE16;
		}
	}
	PUSH_INTOPERAND(value, flags);
	// Now GotByte = non-binary char
}


// Parse hexadecimal value. It accepts "0" to "9", "a" to "f" and "A" to "F".
// Capital letters will be converted to lowercase letters using the flagtable.
// The current value is stored as soon as a character is read that is none of
// those given above.
static void parse_hexadecimal_value(void)	// Now GotByte = "$" or "x"
{
	char		byte;
	int		go_on,		// continue loop flag
			digits	= -1,	// digit counter
			flags	= MVALUE_GIVEN;
	intval_t	value	= 0;

	do {
		digits++;
		go_on = 0;
		byte = GetByte();
		//	first, convert "A-F" to "a-f"
		byte |= (BYTEFLAGS(byte) & BYTEIS_UPCASE);
		// if digit, add digit value
		if ((byte >= '0') && (byte <= '9')) {
			value = (value << 4) + (byte - '0');
			go_on = 1;	// keep going
		}
		// if legal ("a-f") character, add character value
		if ((byte >= 'a') && (byte <= 'f')) {
			value = (value << 4) + (byte - 'a') + 10;
			go_on = 1;	// keep going
		}
	} while (go_on);
	// set force bits
	if (digits > 2) {
		if (digits > 4) {
			if (value < 65536)
				flags |= MVALUE_FORCE24;
		} else {
			if (value < 256)
				flags |= MVALUE_FORCE16;
		}
	}
	PUSH_INTOPERAND(value, flags);
	// Now GotByte = non-hexadecimal char
}


// parse fractional part of a floating-point value
static void parse_frac_part(int integer_part)	// Now GotByte = first digit after decimal point
{
	double	denominator	= 1,
		fpval		= integer_part;

	// parse digits until no more
	while ((GotByte >= '0') && (GotByte <= '9')) {
		fpval = 10 * fpval + (GotByte & 15);	// this works. it's ASCII.
		denominator *= 10;
		GetByte();
	}
	// FIXME - add possibility to read 'e' and exponent!
	PUSH_FPOPERAND(fpval / denominator, MVALUE_GIVEN);
}


// Parse a decimal value. As decimal values don't use any prefixes, this
// function expects the first digit to be read already. If the first two
// digits are "0x", this function branches to the one for parsing hexadecimal
// values. If a decimal point is read, this function branches to the one for
// parsing floating-point values.
// This function accepts '0' through '9' and one dot ('.') as the decimal
// point. The current value is stored as soon as a character is read that is
// none of those given above. Float usage is only activated when a decimal
// point has been found, so don't expect "100000000000000000000" to work.
// CAUTION: "100000000000000000000.0" won't work either, because when the
// decimal point gets parsed, the integer value will have overflown already.
static void parse_decimal_value(void)	// Now GotByte = first digit
{
	intval_t	intval	= (GotByte & 15);	// this works. it's ASCII.

	GetByte();
	// check for "0b" (binary) and "0x" (hexadecimal) prefixes
	if (intval == 0) {
		if (GotByte == 'b') {
			parse_binary_value();
			return;
		}
		if (GotByte == 'x') {
			parse_hexadecimal_value();
			return;
		}
	}
	// parse digits until no more
	while ((GotByte >= '0') && (GotByte <= '9')) {
		intval = 10 * intval + (GotByte & 15);	// ASCII, see above
		GetByte();
	}
	// check whether it's a float
	if (GotByte == '.') {
		// read fractional part
		GetByte();
		parse_frac_part(intval);
	} else {
		PUSH_INTOPERAND(intval, MVALUE_GIVEN);
	}
	// Now GotByte = non-decimal char
}


// Parse octal value. It accepts "0" to "7". The current value is stored as
// soon as a character is read that is none of those given above.
static void parse_octal_value(void)	// Now GotByte = "&"
{
	intval_t	value	= 0;
	int		flags	= MVALUE_GIVEN,
			digits	= 0;	// digit counter

	GetByte();
	while ((GotByte >= '0') && (GotByte <= '7')) {
		value = (value << 3) + (GotByte & 7);	// this works. it's ASCII.
		digits++;
		GetByte();
	}
	// set force bits
	if (digits > 3) {
		if (digits > 6) {
			if (value < 65536)
				flags |= MVALUE_FORCE24;
		} else {
			if (value < 256)
				flags |= MVALUE_FORCE16;
		}
	}
	PUSH_INTOPERAND(value, flags);
	// Now GotByte = non-octal char
}


// Parse program counter ('*')
static void parse_program_counter(void)	// Now GotByte = "*"
{
	struct result_int_t	pc;

	GetByte();
	vcpu_read_pc(&pc);
	PUSH_INTOPERAND(pc.intval, pc.flags | MVALUE_EXISTS);
}


// Parse function call (sin(), cos(), arctan(), ...)
static void parse_function_call(void)
{
	void	*node_body;

	// make lower case version of name in local dynamic buffer
	DynaBuf_to_lower(function_dyna_buf, GlobalDynaBuf);
	// search for tree item
	if (Tree_easy_scan(function_tree, &node_body, function_dyna_buf))
		PUSH_OPERATOR((struct operator*) node_body);
	else
		Throw_error("Unknown function.");
}


// Expect operand or monadic operator (hopefully inlined)
static void expect_operand_or_monadic_operator(void)
{
	struct operator	*operator;
	int		perform_negation;

	SKIPSPACE();
	switch (GotByte) {
	case '+':	// anonymous forward label
		// count plus signs to build name of anonymous label
		DYNABUF_CLEAR(GlobalDynaBuf);
		do
			DYNABUF_APPEND(GlobalDynaBuf, '+');
		while (GetByte() == '+');
		Label_fix_forward_name();
		get_label_value(Section_now->zone);
		goto now_expect_dyadic;

	case '-':	// NEGATION operator or anonymous backward label
		// count minus signs in case it's an anonymous backward label
		perform_negation = FALSE;
		DYNABUF_CLEAR(GlobalDynaBuf);
		do {
			DYNABUF_APPEND(GlobalDynaBuf, '-');
			perform_negation = !perform_negation;
		} while (GetByte() == '-');
		SKIPSPACE();
		if (BYTEFLAGS(GotByte) & FOLLOWS_ANON) {
			DynaBuf_append(GlobalDynaBuf, '\0');
			get_label_value(Section_now->zone);
			goto now_expect_dyadic;
		}

		if (perform_negation)
			PUSH_OPERATOR(&ops_negate);
		// State doesn't change
		break;
// Real monadic operators (state doesn't change, still ExpectMonadic)
	case '!':	// NOT operator
		operator = &ops_not;
		goto get_byte_and_push_monadic;

	case '<':	// LOWBYTE operator
		operator = &ops_lowbyteof;
		goto get_byte_and_push_monadic;

	case '>':	// HIGHBYTE operator
		operator = &ops_highbyteof;
		goto get_byte_and_push_monadic;

	case '^':	// BANKBYTE operator
		operator = &ops_bankbyteof;
		goto get_byte_and_push_monadic;

// Faked monadic operators
	case '(':	// left parenthesis
		operator = &ops_opening;
		goto get_byte_and_push_monadic;

	case ')':	// right parenthesis
		// this makes "()" also throw a syntax error
		Throw_error(exception_syntax);
		alu_state = STATE_ERROR;
		break;
// Operands (values, state changes to ExpectDyadic)
	case '"':	// Quoted character
	case '\'':	// Quoted character
		// Character will be converted using current encoding
		parse_quoted_character(GotByte);
		// Now GotByte = char following closing quote
		goto now_expect_dyadic;

	case '%':	// Binary value
		parse_binary_value();	// Now GotByte = non-binary char
		goto now_expect_dyadic;

	case '&':	// Octal value
		parse_octal_value();	// Now GotByte = non-octal char
		goto now_expect_dyadic;

	case '$':	// Hexadecimal value
		parse_hexadecimal_value();
		// Now GotByte = non-hexadecimal char
		goto now_expect_dyadic;

	case '*':	// Program counter
		parse_program_counter();
		// Now GotByte = char after closing quote
		goto now_expect_dyadic;

// FIXME - find a way to tell decimal point and LOCAL_PREFIX apart!
	case '.':	// Local label or fractional part of float value
		GetByte();	// start after '.'
		// check for fractional part of float value
		if ((GotByte >= '0') && (GotByte <= '9')) {
			parse_frac_part(0);
			// Now GotByte = non-decimal char
			goto now_expect_dyadic;
		}

		if (Input_read_keyword()) {
			// Now GotByte = illegal char
			get_label_value(Section_now->zone);
			goto now_expect_dyadic;
		}

		alu_state = STATE_ERROR;
		break;
	// Decimal values and global labels
	default:	// all other characters
		if ((GotByte >= '0') && (GotByte <= '9')) {
			parse_decimal_value();
			// Now GotByte = non-decimal char
			goto now_expect_dyadic;
		}

		if (BYTEFLAGS(GotByte) & STARTS_KEYWORD) {
			register int	length;
			// Read global label (or "NOT")
			length = Input_read_keyword();
			// Now GotByte = illegal char
			// Check for NOT. Okay, it's hardcoded,
			// but so what? Sue me...
			if ((length == 3)
			&& ((GlobalDynaBuf->buffer[0] | 32) == 'n')
			&& ((GlobalDynaBuf->buffer[1] | 32) == 'o')
			&& ((GlobalDynaBuf->buffer[2] | 32) == 't')) {
				PUSH_OPERATOR(&ops_not);
				// state doesn't change
			} else {
				if (GotByte == '(') {
					parse_function_call();
				} else {
					get_label_value(ZONE_GLOBAL);
					goto now_expect_dyadic;
				}

			}
		} else {
			// illegal character read - so don't go on
			PUSH_INTOPERAND(0, 0);
			// push pseudo value, EXISTS flag is clear
			if (operator_stack[operator_sp-1] == &ops_return) {
				PUSH_OPERATOR(&ops_end);
				alu_state = STATE_TRY_TO_REDUCE_STACKS;
			} else {
				Throw_error(exception_syntax);
				alu_state = STATE_ERROR;
			}
		}
		break;

// no other possibilities, so here are the shared endings

get_byte_and_push_monadic:
		GetByte();
		PUSH_OPERATOR(operator);
		// State doesn't change
		break;

now_expect_dyadic:
		alu_state = STATE_EXPECT_DYADIC_OPERATOR;
		break;
	}
}


// Expect dyadic operator (hopefully inlined)
static void expect_dyadic_operator(void)
{
	void		*node_body;
	struct operator	*operator;

	SKIPSPACE();
	switch (GotByte) {
// Single-character dyadic operators
	case '^':	// "to the power of"
		operator = &ops_powerof;
		goto get_byte_and_push_dyadic;

	case '+':	// add
		operator = &ops_add;
		goto get_byte_and_push_dyadic;

	case '-':	// subtract
		operator = &ops_subtract;
		goto get_byte_and_push_dyadic;

	case '*':	// multiply
		operator = &ops_multiply;
		goto get_byte_and_push_dyadic;

	case '/':	// divide
		operator = &ops_divide;
		goto get_byte_and_push_dyadic;

	case '%':	// modulo
		operator = &ops_modulo;
		goto get_byte_and_push_dyadic;

	case '&':	// bitwise AND
		operator = &ops_and;
		goto get_byte_and_push_dyadic;

	case '|':	// bitwise OR
		operator = &ops_or;
		goto get_byte_and_push_dyadic;

// This part is commented out because there is no XOR character defined
//	case ???:	// bitwise exclusive OR
//		operator = &ops_xor;
//		goto get_byte_and_push_dyadic;

	case '=':	// is equal
		operator = &ops_equals;
		// if it's "==", accept but warn
		if (GetByte() == '=') {
			Throw_first_pass_warning("C-style \"==\" comparison detected.");
			goto get_byte_and_push_dyadic;
		}
		goto push_dyadic;

	case ')':	// closing parenthesis
		operator = &ops_closing;
		goto get_byte_and_push_dyadic;

// Multi-character dyadic operators
	case '!':	// "!="
		if (GetByte() == '=') {
			operator = &ops_notequal;
			goto get_byte_and_push_dyadic;
		}

		Throw_error(exception_syntax);
		alu_state = STATE_ERROR;
		break;
	case '<':	// "<", "<=", "<<" and "<>"
		switch (GetByte()) {
		case '=':	// "<=", less or equal
			operator = &ops_le;
			goto get_byte_and_push_dyadic;

		case '<':	// "<<", shift left
			operator = &ops_sl;
			goto get_byte_and_push_dyadic;

		case '>':	// "<>", not equal
			operator = &ops_notequal;
			goto get_byte_and_push_dyadic;

		default:	// "<", less than
			operator = &ops_lessthan;
			goto push_dyadic;

		}
		//break; unreachable
	case '>':	// ">", ">=", ">>", ">>>" and "><"
		switch (GetByte()) {
		case '=':	// ">=", greater or equal
			operator = &ops_ge;
			goto get_byte_and_push_dyadic;

		case '<':	// "><", not equal
			operator = &ops_notequal;
			goto get_byte_and_push_dyadic;

		case '>':	// ">>" or ">>>", shift right
			operator = &ops_asr;	// arithmetic shift right
			if (GetByte() != '>')
				goto push_dyadic;

			operator = &ops_lsr;	// logical shift right
			goto get_byte_and_push_dyadic;

		default:	// ">", greater than
			operator = &ops_greaterthan;
			goto push_dyadic;

		}
		//break; unreachable
// end of expression or text version of dyadic operator
	default:
		// check string version of operators
		if (BYTEFLAGS(GotByte) & STARTS_KEYWORD) {
			Input_read_and_lower_keyword();
			// Now GotByte = illegal char
			// search for tree item
			if (Tree_easy_scan(operator_tree, &node_body, GlobalDynaBuf)) {
				operator = node_body;
				goto push_dyadic;
			}

			// goto means we don't need an "else {" here
			Throw_error("Unknown operator.");
			alu_state = STATE_ERROR;
		} else {
			operator = &ops_end;
			goto push_dyadic;
		}

	}
	return;

// shared endings
get_byte_and_push_dyadic:
	GetByte();
push_dyadic:
	PUSH_OPERATOR(operator);
	alu_state = STATE_TRY_TO_REDUCE_STACKS;
}


// call C's sin/cos/tan function
static void perform_fp(double (*fn)(double))
{
	if ((RIGHT_FLAGS & MVALUE_IS_FP) == 0) {
		RIGHT_FPVAL = RIGHT_INTVAL;
		RIGHT_FLAGS |= MVALUE_IS_FP;
	}
	RIGHT_FPVAL = fn(RIGHT_FPVAL);
}


// make sure arg is in [-1, 1] range before calling function
static void perform_ranged_fp(double (*fn)(double))
{
	if ((RIGHT_FLAGS & MVALUE_IS_FP) == 0) {
		RIGHT_FPVAL = RIGHT_INTVAL;
		RIGHT_FLAGS |= MVALUE_IS_FP;
	}
	if ((RIGHT_FPVAL >= -1) && (RIGHT_FPVAL <= 1)) {
		RIGHT_FPVAL = fn(RIGHT_FPVAL);
	} else {
		if (RIGHT_FLAGS & MVALUE_DEFINED)
			Throw_error("Argument out of range.");
		RIGHT_FPVAL = 0;
	}
}


// convert right-hand value from fp to int
static void right_fp_to_int()
{
	RIGHT_INTVAL = RIGHT_FPVAL;
	RIGHT_FLAGS &= ~MVALUE_IS_FP;
}


// check both left-hand and right-hand values. if float, convert to int.
// in first pass, throw warning
static void both_ensure_int(int warn)
{
	if (LEFT_FLAGS & MVALUE_IS_FP) {
		LEFT_INTVAL = LEFT_FPVAL;
		LEFT_FLAGS &= ~MVALUE_IS_FP;
	}
	if (RIGHT_FLAGS & MVALUE_IS_FP) {
		RIGHT_INTVAL = RIGHT_FPVAL;
		RIGHT_FLAGS &= ~MVALUE_IS_FP;
	}
	// FIXME - "warn" is not used
	Throw_first_pass_warning("Converted to integer for binary logic operator.");
}


// check both left-hand and right-hand values. if int, convert to float.
static void both_ensure_fp(void)
{
	if ((LEFT_FLAGS & MVALUE_IS_FP) == 0) {
		LEFT_FPVAL = LEFT_INTVAL;
		LEFT_FLAGS |= MVALUE_IS_FP;
	}
	if ((RIGHT_FLAGS & MVALUE_IS_FP) == 0) {
		RIGHT_FPVAL = RIGHT_INTVAL;
		RIGHT_FLAGS |= MVALUE_IS_FP;
	}
}


// make sure both values are float, but mark left one as int (will become one)
static void ensure_int_from_fp(void)
{
	both_ensure_fp();
	LEFT_FLAGS &= ~MVALUE_IS_FP;
}


// Try to reduce stacks by performing high-priority operations
static void try_to_reduce_stacks(int *open_parentheses)
{
	if (operator_sp < 2) {
		alu_state = STATE_EXPECT_OPERAND_OR_MONADIC_OPERATOR;
		return;
	}

	// previous operator has lower piority than current one? then do nothing.
	if (operator_stack[operator_sp - 2]->priority_and_associativity < operator_stack[operator_sp - 1]->priority_and_associativity) {
		alu_state = STATE_EXPECT_OPERAND_OR_MONADIC_OPERATOR;
		return;
	}

	// previous operator has same priority as current one? then check associativity
	if ((operator_stack[operator_sp - 2]->priority_and_associativity == operator_stack[operator_sp - 1]->priority_and_associativity)
	&& IS_RIGHT_ASSOCIATIVE(operator_stack[operator_sp - 1]->priority_and_associativity)) {
		alu_state = STATE_EXPECT_OPERAND_OR_MONADIC_OPERATOR;
		return;
	}

	switch (operator_stack[operator_sp - 2]->handle) {
// special (pseudo) operators
	case OPHANDLE_RETURN:
		// don't touch indirect_flag; needed for INDIRECT flag
		operator_sp--;	// decrement operator stack pointer
		alu_state = STATE_END;
		break;
	case OPHANDLE_OPENING:
		indirect_flag = MVALUE_INDIRECT;	// parentheses found
		switch (operator_stack[operator_sp - 1]->handle) {
		case OPHANDLE_CLOSING:	// matching parentheses
			operator_sp -= 2;	// remove both of them
			alu_state = STATE_EXPECT_DYADIC_OPERATOR;
			break;
		case OPHANDLE_END:	// unmatched parenthesis
			(*open_parentheses)++;	// count
			goto RNTLObutDontTouchIndirectFlag;

		default:
			Bug_found("StrangeParenthesis", operator_stack[operator_sp - 1]->handle);
		}
		break;
	case OPHANDLE_CLOSING:
		Throw_error("Too many ')'.");
		goto remove_next_to_last_operator;

// functions
	case OPHANDLE_INT:
		if (RIGHT_FLAGS & MVALUE_IS_FP)
			right_fp_to_int();
		goto remove_next_to_last_operator;

	case OPHANDLE_FLOAT:
		// convert right-hand value from int to fp
		if ((RIGHT_FLAGS & MVALUE_IS_FP) == 0) {
			RIGHT_FPVAL = RIGHT_INTVAL;
			RIGHT_FLAGS |= MVALUE_IS_FP;
		}
		goto remove_next_to_last_operator;

	case OPHANDLE_SIN:
		perform_fp(sin);
		goto remove_next_to_last_operator;

	case OPHANDLE_COS:
		perform_fp(cos);
		goto remove_next_to_last_operator;

	case OPHANDLE_TAN:
		perform_fp(tan);
		goto remove_next_to_last_operator;

	case OPHANDLE_ARCSIN:
		perform_ranged_fp(asin);
		goto remove_next_to_last_operator;

	case OPHANDLE_ARCCOS:
		perform_ranged_fp(acos);
		goto remove_next_to_last_operator;

	case OPHANDLE_ARCTAN:
		perform_fp(atan);
		goto remove_next_to_last_operator;

// monadic operators
	case OPHANDLE_NOT:
		// fp becomes int
		if (RIGHT_FLAGS & MVALUE_IS_FP)
			right_fp_to_int();
		RIGHT_INTVAL = ~(RIGHT_INTVAL);
		RIGHT_FLAGS &= ~MVALUE_ISBYTE;
		goto remove_next_to_last_operator;

	case OPHANDLE_NEGATE:
		// different operations for fp and int
		if (RIGHT_FLAGS & MVALUE_IS_FP)
			RIGHT_FPVAL = -(RIGHT_FPVAL);
		else
			RIGHT_INTVAL = -(RIGHT_INTVAL);
		RIGHT_FLAGS &= ~MVALUE_ISBYTE;
		goto remove_next_to_last_operator;

	case OPHANDLE_LOWBYTEOF:
		// fp becomes int
		if (RIGHT_FLAGS & MVALUE_IS_FP)
			right_fp_to_int();
		RIGHT_INTVAL = (RIGHT_INTVAL) & 255;
		RIGHT_FLAGS |= MVALUE_ISBYTE;
		RIGHT_FLAGS &= ~MVALUE_FORCEBITS;
		goto remove_next_to_last_operator;

	case OPHANDLE_HIGHBYTEOF:
		// fp becomes int
		if (RIGHT_FLAGS & MVALUE_IS_FP)
			right_fp_to_int();
		RIGHT_INTVAL = ((RIGHT_INTVAL) >> 8) & 255;
		RIGHT_FLAGS |= MVALUE_ISBYTE;
		RIGHT_FLAGS &= ~MVALUE_FORCEBITS;
		goto remove_next_to_last_operator;

	case OPHANDLE_BANKBYTEOF:
		// fp becomes int
		if (RIGHT_FLAGS & MVALUE_IS_FP)
			right_fp_to_int();
		RIGHT_INTVAL = ((RIGHT_INTVAL) >> 16) & 255;
		RIGHT_FLAGS |= MVALUE_ISBYTE;
		RIGHT_FLAGS &= ~MVALUE_FORCEBITS;
		goto remove_next_to_last_operator;

// dyadic operators
	case OPHANDLE_POWEROF:
		if ((RIGHT_FLAGS | LEFT_FLAGS) & MVALUE_IS_FP) {
			both_ensure_fp();
			LEFT_FPVAL = pow(LEFT_FPVAL, RIGHT_FPVAL);
			goto handle_flags_and_dec_stacks;
		}

		if (RIGHT_INTVAL >= 0) {
			LEFT_INTVAL = my_pow(LEFT_INTVAL, RIGHT_INTVAL);
		} else {
			if (RIGHT_FLAGS & MVALUE_DEFINED)
				Throw_error("Exponent is negative.");
			LEFT_INTVAL = 0;
		}
		goto handle_flags_and_dec_stacks;

	case OPHANDLE_MULTIPLY:
		if ((RIGHT_FLAGS | LEFT_FLAGS) & MVALUE_IS_FP) {
			both_ensure_fp();
			LEFT_FPVAL *= RIGHT_FPVAL;
		} else {
			LEFT_INTVAL *= RIGHT_INTVAL;
		}
		goto handle_flags_and_dec_stacks;

	case OPHANDLE_DIVIDE:
		if ((RIGHT_FLAGS | LEFT_FLAGS) & MVALUE_IS_FP) {
			both_ensure_fp();
			if (RIGHT_FPVAL) {
				LEFT_FPVAL /= RIGHT_FPVAL;
			} else {
				if (RIGHT_FLAGS & MVALUE_DEFINED)
					Throw_error(exception_div_by_zero);
				LEFT_FPVAL = 0;
			}
		} else {
			if (RIGHT_INTVAL) {
				LEFT_INTVAL /= RIGHT_INTVAL;
			} else {
				if (RIGHT_FLAGS & MVALUE_DEFINED)
					Throw_error(exception_div_by_zero);
				LEFT_INTVAL = 0;
			}
		}
		goto handle_flags_and_dec_stacks;

	case OPHANDLE_INTDIV:
		if ((RIGHT_FLAGS | LEFT_FLAGS) & MVALUE_IS_FP) {
			both_ensure_fp();
			if (RIGHT_FPVAL) {
				LEFT_INTVAL = LEFT_FPVAL / RIGHT_FPVAL;
			} else {
				if (RIGHT_FLAGS & MVALUE_DEFINED)
					Throw_error(exception_div_by_zero);
				LEFT_INTVAL = 0;
			}
			LEFT_FLAGS &= ~MVALUE_IS_FP;
		} else {
			if (RIGHT_INTVAL) {
				LEFT_INTVAL /= RIGHT_INTVAL;
			} else {
				if (RIGHT_FLAGS & MVALUE_DEFINED)
					Throw_error(exception_div_by_zero);
				LEFT_INTVAL = 0;
			}
		}
		goto handle_flags_and_dec_stacks;

	case OPHANDLE_MODULO:
		if ((RIGHT_FLAGS | LEFT_FLAGS) & MVALUE_IS_FP)
			both_ensure_int(FALSE);
		if (RIGHT_INTVAL) {
			LEFT_INTVAL %= RIGHT_INTVAL;
		} else {
			if (RIGHT_FLAGS & MVALUE_DEFINED)
				Throw_error(exception_div_by_zero);
			LEFT_INTVAL = 0;
		}
		goto handle_flags_and_dec_stacks;

	case OPHANDLE_ADD:
		if ((RIGHT_FLAGS | LEFT_FLAGS) & MVALUE_IS_FP) {
			both_ensure_fp();
			LEFT_FPVAL += RIGHT_FPVAL;
		} else {
			LEFT_INTVAL += RIGHT_INTVAL;
		}
		goto handle_flags_and_dec_stacks;

	case OPHANDLE_SUBTRACT:
		if ((RIGHT_FLAGS | LEFT_FLAGS) & MVALUE_IS_FP) {
			both_ensure_fp();
			LEFT_FPVAL -= RIGHT_FPVAL;
		} else {
			LEFT_INTVAL -= RIGHT_INTVAL;
		}
		goto handle_flags_and_dec_stacks;

	case OPHANDLE_SL:
		if (RIGHT_FLAGS & MVALUE_IS_FP)
			right_fp_to_int();
		if (LEFT_FLAGS & MVALUE_IS_FP)
			LEFT_FPVAL *= pow(2.0, RIGHT_INTVAL);
		else
			LEFT_INTVAL <<= RIGHT_INTVAL;
		goto handle_flags_and_dec_stacks;

	case OPHANDLE_ASR:
		if (RIGHT_FLAGS & MVALUE_IS_FP)
			right_fp_to_int();
		if (LEFT_FLAGS & MVALUE_IS_FP)
			LEFT_FPVAL /= (1 << RIGHT_INTVAL);
		else
			LEFT_INTVAL = my_asr(LEFT_INTVAL, RIGHT_INTVAL);
		goto handle_flags_and_dec_stacks;

	case OPHANDLE_LSR:
		// fp become int
		if ((RIGHT_FLAGS | LEFT_FLAGS) & MVALUE_IS_FP)
			both_ensure_int(TRUE);
		LEFT_INTVAL = ((uintval_t) LEFT_INTVAL) >> RIGHT_INTVAL;
		goto handle_flags_and_dec_stacks;

	case OPHANDLE_LE:
		if ((RIGHT_FLAGS | LEFT_FLAGS) & MVALUE_IS_FP) {
			ensure_int_from_fp();
			LEFT_INTVAL = (LEFT_FPVAL <= RIGHT_FPVAL);
		} else {
			LEFT_INTVAL = (LEFT_INTVAL <= RIGHT_INTVAL);
		}
		goto handle_flags_and_dec_stacks;

	case OPHANDLE_LESSTHAN:
		if ((RIGHT_FLAGS | LEFT_FLAGS) & MVALUE_IS_FP) {
			ensure_int_from_fp();
			LEFT_INTVAL = (LEFT_FPVAL < RIGHT_FPVAL);
		} else {
			LEFT_INTVAL = (LEFT_INTVAL < RIGHT_INTVAL);
		}
		goto handle_flags_and_dec_stacks;

	case OPHANDLE_GE:
		if ((RIGHT_FLAGS | LEFT_FLAGS) & MVALUE_IS_FP) {
			ensure_int_from_fp();
			LEFT_INTVAL = (LEFT_FPVAL >= RIGHT_FPVAL);
		} else {
			LEFT_INTVAL = (LEFT_INTVAL >= RIGHT_INTVAL);
		}
		goto handle_flags_and_dec_stacks;

	case OPHANDLE_GREATERTHAN:
		if ((RIGHT_FLAGS | LEFT_FLAGS) & MVALUE_IS_FP) {
			ensure_int_from_fp();
			LEFT_INTVAL = (LEFT_FPVAL > RIGHT_FPVAL);
		} else {
			LEFT_INTVAL = (LEFT_INTVAL > RIGHT_INTVAL);
		}
		goto handle_flags_and_dec_stacks;

	case OPHANDLE_NOTEQUAL:
		if ((RIGHT_FLAGS | LEFT_FLAGS) & MVALUE_IS_FP) {
			ensure_int_from_fp();
			LEFT_INTVAL = (LEFT_FPVAL != RIGHT_FPVAL);
		} else {
			LEFT_INTVAL = (LEFT_INTVAL != RIGHT_INTVAL);
		}
		goto handle_flags_and_dec_stacks;

	case OPHANDLE_EQUALS:
		if ((RIGHT_FLAGS | LEFT_FLAGS) & MVALUE_IS_FP) {
			ensure_int_from_fp();
			LEFT_INTVAL = (LEFT_FPVAL == RIGHT_FPVAL);
		} else {
			LEFT_INTVAL = (LEFT_INTVAL == RIGHT_INTVAL);
		}
		goto handle_flags_and_dec_stacks;

	case OPHANDLE_AND:
		// fp become int
		if ((RIGHT_FLAGS | LEFT_FLAGS) & MVALUE_IS_FP)
			both_ensure_int(TRUE);
		LEFT_INTVAL &= RIGHT_INTVAL;
		goto handle_flags_and_dec_stacks;

	case OPHANDLE_EOR:
		Throw_first_pass_warning("\"EOR\" is deprecated; use \"XOR\" instead.");
		/*FALLTHROUGH*/
	case OPHANDLE_XOR:
		// fp become int
		if ((RIGHT_FLAGS | LEFT_FLAGS) & MVALUE_IS_FP)
			both_ensure_int(TRUE);
		LEFT_INTVAL ^= RIGHT_INTVAL;
		goto handle_flags_and_dec_stacks;

	case OPHANDLE_OR:
		// fp become int
		if ((RIGHT_FLAGS | LEFT_FLAGS) & MVALUE_IS_FP)
			both_ensure_int(TRUE);
		LEFT_INTVAL |= RIGHT_INTVAL;
		goto handle_flags_and_dec_stacks;

	default:
		Bug_found("IllegalOperatorHandle", operator_stack[operator_sp - 2]->handle);
	}
	return;

// shared endings:

// entry point for dyadic operators
handle_flags_and_dec_stacks:
	// Handle flags and decrement value stack pointer
	// "OR" EXISTS, UNSURE and FORCEBIT flags
	LEFT_FLAGS |= RIGHT_FLAGS &
		(MVALUE_EXISTS|MVALUE_UNSURE|MVALUE_FORCEBITS);
	// "AND" DEFINED flag
	LEFT_FLAGS &= (RIGHT_FLAGS | ~MVALUE_DEFINED);
	LEFT_FLAGS &= ~MVALUE_ISBYTE;	// clear ISBYTE flag
	operand_sp--;
// entry point for monadic operators
remove_next_to_last_operator:
	// toplevel operation was something other than parentheses
	indirect_flag = 0;
// entry point for '(' operator (has set indirect_flag, so don't clear now)
RNTLObutDontTouchIndirectFlag:
	// Remove operator and shift down next one
	operator_stack[operator_sp-2] = operator_stack[operator_sp-1];
	operator_sp--;	// decrement operator stack pointer
}


// The core of it. Returns number of parentheses left open.
// FIXME - make state machine using function pointers? or too slow?
static int parse_expression(struct result_t *result)
{
	int	open_parentheses	= 0;

	operator_sp = 0;	// operator stack pointer
	operand_sp = 0;	// value stack pointer
	// begin by reading value (or monadic operator)
	alu_state = STATE_EXPECT_OPERAND_OR_MONADIC_OPERATOR;
	indirect_flag = 0;	// Contains either 0 or MVALUE_INDIRECT
	PUSH_OPERATOR(&ops_return);
	do {
		// check stack sizes. enlarge if needed
		if (operator_sp >= operator_stk_size)
			enlarge_operator_stack();
		if (operand_sp >= operand_stk_size)
			enlarge_operand_stack();
		switch (alu_state) {
		case STATE_EXPECT_OPERAND_OR_MONADIC_OPERATOR:
			expect_operand_or_monadic_operator();
			break;
		case STATE_EXPECT_DYADIC_OPERATOR:
			expect_dyadic_operator();
			break;	// no fallthrough; state might
			// have been changed to END or ERROR
		case STATE_TRY_TO_REDUCE_STACKS:
			try_to_reduce_stacks(&open_parentheses);
			break;
		case STATE_MAX_GO_ON:	// suppress
		case STATE_ERROR:	// compiler
		case STATE_END:		// warnings
			break;
		}
	} while (alu_state < STATE_MAX_GO_ON);
	// done. check state.
	if (alu_state == STATE_END) {
		// check for bugs
		if (operand_sp != 1)
			Bug_found("OperandStackNotEmpty", operand_sp);
		if (operator_sp != 1)
			Bug_found("OperatorStackNotEmpty", operator_sp);
		// copy result
		*result = operand_stack[0];
		result->flags |= indirect_flag;	// OR indirect flag
		// only allow *one* force bit
		if (result->flags & MVALUE_FORCE24)
			result->flags &= ~(MVALUE_FORCE16 | MVALUE_FORCE08);
		else if (result->flags & MVALUE_FORCE16)
			result->flags &= ~MVALUE_FORCE08;
		// if there was nothing to parse, mark as undefined
		// (so ALU_defined_int() can react)
		if ((result->flags & MVALUE_EXISTS) == 0)
			result->flags &= ~MVALUE_DEFINED;
		// do some checks depending on int/float
		if (result->flags & MVALUE_IS_FP) {
/*float*/		// if undefined, return zero
			if ((result->flags & MVALUE_DEFINED) == 0)
				result->val.fpval = 0;
			// if value is sure, check to set ISBYTE
			else if (((result->flags & MVALUE_UNSURE) == 0)
			&& (result->val.fpval <= 255.0)
			&& (result->val.fpval >= -128.0))
				result->flags |= MVALUE_ISBYTE;
		} else {
/*int*/			// if undefined, return zero
			if ((result->flags & MVALUE_DEFINED) == 0)
				result->val.intval = 0;
			// if value is sure, check to set ISBYTE
			else if (((result->flags & MVALUE_UNSURE) == 0)
			&& (result->val.intval <= 255)
			&& (result->val.intval >= -128))
				result->flags |= MVALUE_ISBYTE;
		}
	} else {
		// State is STATE_ERROR. But actually, nobody cares.
		// ...errors have already been reported anyway. :)
	}
	// return number of open (unmatched) parentheses
	return open_parentheses;
}


// These functions handle numerical expressions. There are operators for
// arithmetic, logic, shift and comparison operations.
// There are several different ways to call the core function:
// intval_t ALU_any_int(void);
//		returns int value (0 if result was undefined)
// intval_t ALU_defined_int(void);
//		returns int value
//		if result was undefined, serious error is thrown
// void ALU_int_result(result_int_t*);
//		stores int value and flags (floats are transformed to int)
// void ALU_any_result(result_t*);
//		stores value and flags (result may be either int or float)
// int ALU_liberal_int(result_int_t*);
//		stores int value and flags. allows one '(' too many (for x-
//		indirect addressing). returns number of additional '(' (1 or 0).
// int ALU_optional_defined_int(intval_t*);
//		stores int value if given. Returns whether stored.
//		Throws error if undefined.

// return int value (if result is undefined, returns zero)
// If the result's "exists" flag is clear (=empty expression), it throws an
// error.
// If the result's "defined" flag is clear, result_is_undefined() is called.
intval_t ALU_any_int(void)
{
	struct result_t	result;

	if (parse_expression(&result))
		Throw_error(exception_paren_open);
	if ((result.flags & MVALUE_EXISTS) == 0)
		Throw_error(exception_no_value);
	else if ((result.flags & MVALUE_DEFINED) == 0)
		result_is_undefined();
	if (result.flags & MVALUE_IS_FP)
		return result.val.fpval;
	else
		return result.val.intval;
}


// return int value (if result is undefined, serious error is thrown)
intval_t ALU_defined_int(void)
{
	struct result_t	result;

	if (parse_expression(&result))
		Throw_error(exception_paren_open);
	if ((result.flags & MVALUE_DEFINED) == 0)
		Throw_serious_error(exception_undefined);
	if (result.flags & MVALUE_IS_FP)
		return result.val.fpval;
	else
		return result.val.intval;
}


// Store int value if given. Returns whether stored. Throws error if undefined.
// This function needs either a defined value or no expression at all. So
// empty expressions are accepted, but undefined ones are not.
// If the result's "defined" flag is clear and the "exists" flag is set, it
// throws a serious error and therefore stops assembly.
int ALU_optional_defined_int(intval_t *target)
{
	struct result_t	result;

	if (parse_expression(&result))
		Throw_error(exception_paren_open);
	if ((result.flags & MVALUE_GIVEN) == MVALUE_EXISTS)
		Throw_serious_error(exception_undefined);
	if ((result.flags & MVALUE_EXISTS) == 0)
		return 0;
	// something was given, so store
	if (result.flags & MVALUE_IS_FP)
		*target = result.val.fpval;
	else
		*target = result.val.intval;
	return 1;
}


// Store int value and flags (floats are transformed to int)
// It the result's "exists" flag is clear (=empty expression), it throws an
// error.
// If the result's "defined" flag is clear, result_is_undefined() is called.
void ALU_int_result(struct result_int_t *intresult)
{
	struct result_t	result;

	if (parse_expression(&result))
		Throw_error(exception_paren_open);
	if ((result.flags & MVALUE_EXISTS) == 0)
		Throw_error(exception_no_value);
	else if ((result.flags & MVALUE_DEFINED) == 0)
		result_is_undefined();
	if (result.flags & MVALUE_IS_FP) {
		intresult->intval = result.val.fpval;
		intresult->flags = result.flags & ~MVALUE_IS_FP;
	} else {
		intresult->intval = result.val.intval;
		intresult->flags = result.flags;
	}
}


// Store int value and flags.
// This function allows for one '(' too many. Needed when parsing indirect
// addressing modes where internal indices have to be possible. Returns number
// of parentheses still open (either 0 or 1).
int ALU_liberal_int(struct result_int_t *intresult)
{
	struct result_t	result;
	int		parentheses_still_open;

	parentheses_still_open = parse_expression(&result);
	if (parentheses_still_open > 1) {
		parentheses_still_open = 0;
		Throw_error(exception_paren_open);
	}
	if ((result.flags & MVALUE_EXISTS)
	&& ((result.flags & MVALUE_DEFINED) == 0))
		result_is_undefined();
	if (result.flags & MVALUE_IS_FP) {
		intresult->intval = result.val.fpval;
		intresult->flags = result.flags & ~MVALUE_IS_FP;
	} else {
		intresult->intval = result.val.intval;
		intresult->flags = result.flags;
	}
	return parentheses_still_open;
}


// Store value and flags (result may be either int or float)
// It the result's "exists" flag is clear (=empty expression), it throws an
// error.
// If the result's "defined" flag is clear, result_is_undefined() is called.
void ALU_any_result(struct result_t *result)
{
	if (parse_expression(result))
		Throw_error(exception_paren_open);
	if ((result->flags & MVALUE_EXISTS) == 0)
		Throw_error(exception_no_value);
	else if ((result->flags & MVALUE_DEFINED) == 0)
		result_is_undefined();
}