/*
 * The constant field is a boolean flag marking which subexpressions are
 * completely known at compile time, and are eligible for computing then
 * rather than waiting until run time.
 */

/*
 * Each lexeme belongs to one of four categories, which determine its place in
 * the parse tree. We use the two high bits of the (unsigned char) value to
 * store a NODE_TYPE code.
 */

#define NODE_TYPE	0xC0

/*
 * The four category values are LEAF, UNARY, and BINARY, explained below, and
 * "uncategorized", which is used either temporarily, until context determines
 * which of the other three categories is correct, or for lexemes like
 * INVALID, which aren't really lexemes at all, but indicators of a parsing
 * error. Note that the codes must be distinct to distinguish categories, but
 * need not take the form of a bit array.
 */








#define BINARY		0x40	/* This lexeme is a binary operator. An OpNode
				 * representing it should go into the parse
				 * tree, and two operands should be parsed for
				 * it in the expression. */
#define UNARY		0x80	/* This lexeme is a unary operator. An OpNode
				 * representing it should go into the parse
				 * tree, and one operand should be parsed for
				 * it in the expression. */
#define LEAF		0xC0	/* This lexeme is a leaf operand in the parse
				 * tree. No OpNode will be placed in the tree
				 * for it. Either a literal value will be
				 * appended to the list of literals in this
				 * expression, or appropriate Tcl_Tokens will
				 * be appended in a Tcl_Parse struct to
				 * represent those leaves that require some
				 * form of substitution. */



/* Uncategorized lexemes */

#define PLUS		1	/* Ambiguous. Resolves to UNARY_PLUS or
				 * BINARY_PLUS according to context. */
#define MINUS		2	/* Ambiguous. Resolves to UNARY_MINUS or
				 * BINARY_MINUS according to context. */
#define BAREWORD	3	/* Ambiguous. Resolves to BOOLEAN or to
				 * FUNCTION or a parse error according to
				 * context and value. */
#define INCOMPLETE	4	/* A parse error. Used only when the single
				 * "=" is encountered.  */
#define INVALID		5	/* A parse error. Used when any punctuation
				 * appears that's not a supported operator. */
#define COMMENT		6	/* Comment. Lasts to end of line or end of
				 * expression, whichever comes first. */

/* Leaf lexemes */

#define NUMBER		(LEAF | 1)
				/* For literal numbers */
#define SCRIPT		(LEAF | 2)
				/* Script substitution; [foo] */
#define BOOLEAN		(LEAF | BAREWORD)
				/* For literal booleans */
#define BRACED		(LEAF | 4)
				/* Braced string; {foo bar} */
#define VARIABLE	(LEAF | 5)
				/* Variable substitution; $x */
#define QUOTED		(LEAF | 6)
				/* Quoted string; "foo $bar [soom]" */
#define EMPTY		(LEAF | 7)
				/* Used only for an empty argument list to a
				 * function. Represents the empty string
				 * within parens in the expression: rand() */

/* Unary operator lexemes */

#define UNARY_PLUS	(UNARY | PLUS)
#define UNARY_MINUS	(UNARY | MINUS)
#define FUNCTION	(UNARY | BAREWORD)
				/* This is a bit of "creative interpretation"
				 * on the part of the parser. A function call
				 * is parsed into the parse tree according to
				 * the perspective that the function name is a
				 * unary operator and its argument list,
				 * enclosed in parens, is its operand. The
				 * additional requirements not implied
				 * generally by treatment as a unary operator
				 * -- for example, the requirement that the
				 * operand be enclosed in parens -- are hard
				 * coded in the relevant portions of
				 * ParseExpr(). We trade off the need to
				 * include such exceptional handling in the
				 * code against the need we would otherwise
				 * have for more lexeme categories. */
#define START		(UNARY | 4)
				/* This lexeme isn't parsed from the
				 * expression text at all. It represents the
				 * start of the expression and sits at the
				 * root of the parse tree where it serves as
				 * the start/end point of traversals. */
#define OPEN_PAREN	(UNARY | 5)
				/* Another bit of creative interpretation,
				 * where we treat "(" as a unary operator with
				 * the sub-expression between it and its
				 * matching ")" as its operand. See
				 * CLOSE_PAREN below. */
#define NOT		(UNARY | 6)
#define BIT_NOT		(UNARY | 7)

/* Binary operator lexemes */

#define BINARY_PLUS	(BINARY |  PLUS)
#define BINARY_MINUS	(BINARY |  MINUS)
#define COMMA		(BINARY |  3)
				/* The "," operator is a low precedence binary
				 * operator that separates the arguments in a
				 * function call. The additional constraint
				 * that this operator can only legally appear
				 * at the right places within a function call
				 * argument list are hard coded within
				 * ParseExpr().  */
#define MULT		(BINARY |  4)
#define DIVIDE		(BINARY |  5)
#define MOD		(BINARY |  6)
#define LESS		(BINARY |  7)
#define GREATER		(BINARY |  8)
#define BIT_AND		(BINARY |  9)
#define BIT_XOR		(BINARY | 10)
#define BIT_OR		(BINARY | 11)
#define QUESTION	(BINARY | 12)
				/* These two lexemes make up the */
#define COLON		(BINARY | 13)
				/* ternary conditional operator, $x ? $y : $z.
				 * We treat them as two binary operators to
				 * avoid another lexeme category, and code the
				 * additional constraints directly in
				 * ParseExpr(). For instance, the right
				 * operand of a "?" operator must be a ":"
				 * operator. */
#define LEFT_SHIFT	(BINARY | 14)
#define RIGHT_SHIFT	(BINARY | 15)
#define LEQ		(BINARY | 16)
#define GEQ		(BINARY | 17)
#define EQUAL		(BINARY | 18)
#define NEQ		(BINARY | 19)
#define AND		(BINARY | 20)
#define OR		(BINARY | 21)
#define STREQ		(BINARY | 22)
#define STRNEQ		(BINARY | 23)
#define EXPON		(BINARY | 24)
				/* Unlike the other binary operators, EXPON is
				 * right associative and this distinction is
				 * coded directly in ParseExpr(). */
#define IN_LIST		(BINARY | 25)
#define NOT_IN_LIST	(BINARY | 26)
#define CLOSE_PAREN	(BINARY | 27)
				/* By categorizing the CLOSE_PAREN lexeme as a
				 * BINARY operator, the normal parsing rules
				 * for binary operators assure that a close
				 * paren will not directly follow another
				 * operator, and the machinery already in
				 * place to connect operands to operators
				 * according to precedence performs most of
				 * the work of matching open and close parens
				 * for us. In the end though, a close paren is
				 * not really a binary operator, and some
				 * special coding in ParseExpr() make sure we
				 * never put an actual CLOSE_PAREN node in the
				 * parse tree. The sub-expression between
				 * parens becomes the single argument of the
				 * matching OPEN_PAREN unary operator. */
#define STR_LT		(BINARY | 28)
#define STR_GT		(BINARY | 29)
#define STR_LEQ		(BINARY | 30)
#define STR_GEQ		(BINARY | 31)
#define END		(BINARY | 32)
				/* This lexeme represents the end of the
				 * string being parsed. Treating it as a
				 * binary operator follows the same logic as
				 * the CLOSE_PAREN lexeme and END pairs with
				 * START, in the same way that CLOSE_PAREN
				 * pairs with OPEN_PAREN. */


/*
 * When ParseExpr() builds the parse tree it must choose which operands to
 * connect to which operators.  This is done according to operator precedence.
 * The greater an operator's precedence the greater claim it has to link to an
 * available operand.  The Precedence enumeration lists the precedence values
 * used by Tcl expression operators, from lowest to highest claim.  Each

		     * name, and there's no place in the parse tree to store
		     * it, so we keep a separate list of all the function
		     * names we've parsed in the order we found them.
		     */

		    Tcl_ListObjAppendElement(NULL, funcList, literal);
		} else if (Tcl_GetBooleanFromObj(NULL,literal,&b) == TCL_OK) {
		    lexeme = BOOLEAN;
		} else {
		    /*
		     * Tricky case: see test expr-62.10
		     */

		    int scanned2 = scanned;
		    do {

		scanned = 0;
		insertMark = 1;

		/*
		 * Free any literal to avoid a memleak.
		 */

		if ((lexeme == NUMBER) || (lexeme == BOOLEAN)) {
		    Tcl_DecrRefCount(literal);
		}
		goto error;
	    }

	    switch (lexeme) {
	    case NUMBER:
	    case BOOLEAN:
		/*
		 * TODO: Consider using a dict or hash to collapse all
		 * duplicate literals into a single representative value.
		 * (Like what is done with [split $s {}]).
		 * Pro:	~75% memory saving on expressions like
		 *	{1+1+1+1+1+.....+1} (Convert "pointer + Tcl_Obj" cost
		 *	to "pointer" cost only)