--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/lwlink/expr.h	Wed Jan 28 05:59:14 2009 +0000
@@ -0,0 +1,107 @@
+/*
+expr.h
+Copyright © 2009 William Astle
+
+This file is part of LWLINK.
+
+LWLINK is free software: you can redistribute it and/or modify it under the
+terms of the GNU General Public License as published by the Free Software
+Foundation, either version 3 of the License, or (at your option) any later
+version.
+
+This program is distributed in the hope that it will be useful, but WITHOUT
+ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
+more details.
+
+You should have received a copy of the GNU General Public License along with
+this program. If not, see <http://www.gnu.org/licenses/>.
+*/
+
+/*
+Definitions for expression evaluator
+*/
+
+#ifndef __expr_h_seen__
+#define __expr_h_seen__
+
+#ifndef __expr_c_seen__
+#define __expr_E__ extern
+#else
+#define __expr_E__
+#endif
+
+// term types
+#define LW_TERM_NONE		0
+#define LW_TERM_OPER		1	// an operator
+#define LW_TERM_INT		2	// 32 bit signed integer
+#define LW_TERM_SYM		3	// symbol reference
+
+// operator types
+#define LW_OPER_NONE		0
+#define LW_OPER_PLUS		1	// +
+#define LW_OPER_MINUS	2	// -
+#define LW_OPER_TIMES	3	// *
+#define LW_OPER_DIVIDE	4	// /
+#define LW_OPER_MOD		5	// %
+#define LW_OPER_INTDIV	6	// \ (don't end line with \)
+#define LW_OPER_BWAND	7	// bitwise AND
+#define LW_OPER_BWOR		8	// bitwise OR
+#define LW_OPER_BWXOR	9	// bitwise XOR
+#define LW_OPER_AND		10	// boolean AND
+#define LW_OPER_OR		11	// boolean OR
+#define LW_OPER_NEG		12	// - unary negation (2's complement)
+#define LW_OPER_COM		13	// ^ unary 1's complement
+
+
+// term structure
+typedef struct lw_expr_term_s
+{
+	int term_type;		// type of term (see above)
+	char *symbol;		// name of a symbol
+	int value;			// value of the term (int) or operator number (OPER)
+} lw_expr_term_t;
+
+// type for an expression evaluation stack
+typedef struct lw_expr_stack_node_s lw_expr_stack_node_t;
+struct lw_expr_stack_node_s
+{
+	lw_expr_term_t		*term;
+	lw_expr_stack_node_t	*prev;
+	lw_expr_stack_node_t	*next;	
+};
+
+typedef struct lw_expr_stack_s
+{
+	lw_expr_stack_node_t *head;
+	lw_expr_stack_node_t *tail;
+} lw_expr_stack_t;
+
+__expr_E__ void lw_expr_term_free(lw_expr_term_t *t);
+__expr_E__ lw_expr_term_t *lw_expr_term_create_oper(int oper);
+__expr_E__ lw_expr_term_t *lw_expr_term_create_sym(char *sym, int symtype);
+__expr_E__ lw_expr_term_t *lw_expr_term_create_int(int val);
+__expr_E__ lw_expr_term_t *lw_expr_term_dup(lw_expr_term_t *t);
+
+__expr_E__ void lw_expr_stack_free(lw_expr_stack_t *s);
+__expr_E__ lw_expr_stack_t *lw_expr_stack_create(void);
+
+__expr_E__ void lw_expr_stack_push(lw_expr_stack_t *s, lw_expr_term_t *t);
+__expr_E__ lw_expr_term_t *lw_expr_stack_pop(lw_expr_stack_t *s);
+
+// simplify expression
+__expr_E__ int lw_expr_reval(lw_expr_stack_t *s, lw_expr_stack_t *(*sfunc)(char *sym, int symtype, void *state), void *state);
+
+// useful macros
+// is the expression "simple" (one term)?
+#define lw_expr_is_simple(s) ((s) -> head == (s) -> tail)
+
+// is the expression constant?
+#define lw_expr_is_constant(s) (lw_expr_is_simple(s) && (!((s) -> head) || (s) -> head -> term -> term_type == LW_TERM_INT))
+
+// get the constant value of an expression or 0 if not constant
+#define lw_expr_get_value(s) (lw_expr_is_constant(s) ? ((s) -> head ? (s) -> head -> term -> value : 0) : 0)
+
+#undef __expr_E__
+
+#endif // __expr_h_seen__