ubstituted into the word. The token
 *				includes the enclosing brackets. NumComponents
 *				is always 0.
 * TCL_TOKEN_VARIABLE -		The token describes a variable substitution,
 *				including the dollar sign, variable name, and
 *				array index (if there is one) up through the
 *				right parentheses. NumComponents tells how
 *				many additional tokens follow to represent the
 *				variable name. The first token will be a
 *				TCL_TOKEN_TEXT token that describes the
 *				variable name. If the variable is an array
 *				reference then there will be one or more
 *				additional tokens, of type TCL_TOKEN_TEXT,
 *				TCL_TOKEN_BS, TCL_TOKEN_COMMAND, and
 *				TCL_TOKEN_VARIABLE, that describe the array
 *				index; numComponents counts the total number
 *				of nested tokens that make up the variable
 *				reference, including sub-tokens of
 *				TCL_TOKEN_VARIABLE tokens.
 * TCL_TOKEN_SUB_EXPR -		The token describes one subexpression of an
 *				expression, from the first non-blank character
 *				of the subexpression up to but not including
 *				the space, brace, or bracket that terminates
 *				the subexpression. NumComponents counts the
 *				total number of following subtokens that make
 *				up the subexpression; this includes all
 *				subtokens for any nested TCL_TOKEN_SUB_EXPR
 *				tokens. For example, a numeric value used as a
 *				primitive operand is described by a
 *				TCL_TOKEN_SUB_EXPR token followed by a
 *				TCL_TOKEN_TEXT token. A binary subexpression
 *				is described by a TCL_TOKEN_SUB_EXPR token
 *				followed by the TCL_TOKEN_OPERATOR token for
 *				the operator, then TCL_TOKEN_SUB_EXPR tokens
 *				for the left then the right operands.
 * TCL_TOKEN_OPERATOR -		The token describes one expression operator.
 *				An operator might be the name of a math
 *				function such as "abs". A TCL_TOKEN_OPERATOR
 *				token is always preceded by one
 *				TCL_TOKEN_SUB_EXPR token for the operator's
 *				subexpression, and is followed by zero or more
 *				TCL_TOKEN_SUB_EXPR tokens for the operator's
 *				operands. NumComponents is always 0.
 * TCL_TOKEN_EXPAND_WORD -	This token is just like TCL_TOKEN_WORD except
 *				that it marks a word that began with the
 *				literal character prefix "{*}". This word is
 *				marked to be expanded - that is, broken into
 *				words after substitution is complete.
 */

#define TCL_TOKEN_WORD		1
#define TCL_TOKEN_SIMPLE_WORD	2
#define TCL_TOKEN_TEXT		4
#define TCL_TOKEN_BS		8
#define TCL_TOKEN_COMMAND	16
#define TCL_TOKEN_VARIABLE	32
#define TCL_TOKEN_SUB_EXPR	64
#define TCL_TOKEN_OPERATOR	128
#define TCL_TOKEN_EXPAND_WORD	256

/*
 * Parsing error types. On any parsing error, one of these values will be
 * stored in the error field of the Tcl_Parse structure defined below.
 */

#define TCL_PARSE_SUCCESS		0
#define TCL_PARSE_QUOTE_EXTRA		1
#define TCL_PARSE_BRACE_EXTRA		2
#define TCL_PARSE_MISSING_BRACE		3
#define TCL_PARSE_MISSING_BRACKET	4
#define TCL_PARSE_MISSING_PAREN		5
#define TCL_PARSE_MISSING_QUOTE		6
#define TCL_PARSE_MISSING_VAR_BRACE	7
#define TCL_PARSE_SYNTAX		8
#define TCL_PARSE_BAD_NUMBER		9

/*
 * A structure of the following type is filled in by Tcl_ParseCommand. It
 * describes a single command parsed from an input string.
 */

#define NUM_STATIC_TOKENS 20

typedef struct Tcl_Parse {
    const char *commentStart;	/* Pointer to # that begins the first of one
				 * or more comments preceding the command. */
    int commentSize;		/* Number of bytes in comments (up through
				 * newline character that terminates the last
				 * comment). If there were no comments, this
				 * field is 0. */
    const char *commandStart;	/* First character in first word of
				 * command. */
    int commandSize;		/* Number of bytes in command, including first
				 * character of first word, up through the
				 * terminating newline, close bracket, or
				 * semicolon. */
    int numWords;		/* Total number of words in command. May be
				 * 0. */
    Tcl_Token *tokenPtr;	/* Pointer to first token representing the
				 * words of the command. Initially points to
				 * staticTokens, but may change to point to
				 * malloc-ed space if command exceeds space in
				 * staticTokens. */
    int numTokens;		/* Total number of tokens in command. */
    int tokensAvailable;	/* Total number of tokens available at
				 * *tokenPtr. */
    int errorType;		/* One of the parsing error types defined
				 * above. */

    /*
     * The fields below are intended only for the private use of the parser.
     * They should not be used by functions that invoke Tcl_ParseCommand.
     */

    const char *string;		/* The original command string passed to
				 * Tcl_ParseCommand. */
    const char *end;		/* Points to the character just after the last
				 * one in the command string. */
    Tcl_Interp *interp;		/* Interpreter to use for error reporting, or
				 * NULL. */
    const char *term;		/* Points to character in string that
				 * terminated most recent token. Filled in by
				 * ParseTokens. If an error occurs, points to
				 * beginning of region where the error
				 * occurred (e.g. the open brace if the close
				 * brace is missing). */
    int incomplete;		/* This field is set to 1 by Tcl_ParseCommand
				 * if the command appears to be incomplete.
				 * This information is used by
				 * Tcl_CommandComplete. */
    Tcl_Token staticTokens[NUM_STATIC_TOKENS];
				/* Initial space for tokens for command. This
				 * space should be large enough to accommodate
				 * most commands; dynamic space is allocated
				 * for very large commands that don't fit
				 * here. */
} Tcl_Parse;