--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/lwval.h	Thu Oct 23 03:37:48 2008 +0000
@@ -0,0 +1,111 @@
+/*
+lwval.h
+Copyright © 2008 William Astle
+
+This file is part of LWASM.
+
+LWASM 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/>.
+*/
+
+/*
+This file contains definitions associated with the expression evaluator used
+by LWASM.
+
+The core of the entire expression handler is the opaque type LWVAL, pointers
+to which are passed around to keep track of values. A value may be a simple
+integer or it could be a more complex expression linked by operators or it
+could be a polynomial expression. Simple integers are merely a degenerate
+case of polynomials.
+
+The package understands the following operations:
+
+addition
+subtraction
+multiplication
+division
+modulus
+parentheses
+unary negation
+unary "positive"
+bitwise and
+bitwise or
+bitwise not (1's complement)
+bitwise exclusive or
+
+Infix operators can be expressed as LWVAL <op> LWVAL. Thus, the order of
+operations is only relevant when initially parsing the expression. The order
+of evaluation is determined by what appears on either side of the <op> as
+an LWVAL may be an expression.
+*/
+
+#ifndef __lwval_h_seen__
+#define __lwval_h_seen__
+
+typedef struct lwval LWVAL;
+
+struct lwval_dt_expr
+{
+	LWVAL *v1;						// first value
+	LWVAL *v2;						// second value
+	int op;							// operator
+};
+
+union lwval_dt
+{
+	int lwval_int;					// integer type data
+	char *lwval_var;				// pointer to variable name
+	struct lwval_dt_expr expr;		// expression
+};
+
+enum
+{
+	LWVAL_TYPE_UNDEF,				// undefined
+	LWVAL_TYPE_NAN,					// not a number
+	LWVAL_TYPE_INT,					// integer
+	LWVAL_TYPE_VAR,					// variable (symbol)
+	LWVAL_TYPE_EXPR,				// expression
+	LWVAL_TYPE_ERR					// error
+};
+
+struct lwval
+{
+	int lwval_type;					// data type
+	union lwval_dt dt;				// type specific stuff
+};
+
+#ifndef __lwval_c_seen__
+#define EE extern
+#else
+#define EE
+#endif
+
+EE LWVAL *lwval_construct_int(int value);
+EE LWVAL *lwval_construct_err(int errno);
+EE LWVAL *lwval_construct_nan(void);
+EE LWVAL *lwval_construct_expr(LWVAL *v1, LWVAL *v2, int op);
+EE LWVAL *lwval_construct_undef(void);
+EE void lwval_clear(LWVAL *value);
+EE void lwval_destroy(LWVAL *value);
+EE void lwval_dup(LWVAL *v1, LWVAL *v2);
+
+// operators - operate on v1 and v2 in order, result goes into
+// v1; return v1
+EE LWVAL *lwval_add(LWVAL *v1, LWVAL *v2);
+EE LWVAL *lwval_sub(LWVAL *v1, LWVAL *v2);
+EE LWVAL *lwval_mul(LWVAL *v1, LWVAL *v2);
+EE LWVAL *lwval_div(LWVAL *v1, LWVAL *v2);
+EE LWVAL *lwval_mod(LWVAL *v1, LWVAL *v2);
+EE LWVAL *lwval_neg(LWVAL *v1);
+
+#endif //__lwval_h_seen__