diff options
| -rw-r--r-- | generic/tclCompExpr.c | 65 |
1 files changed, 55 insertions, 10 deletions
diff --git a/generic/tclCompExpr.c b/generic/tclCompExpr.c index 9028fa4..b178a2a 100644 --- a/generic/tclCompExpr.c +++ b/generic/tclCompExpr.c @@ -10,7 +10,7 @@ * See the file "license.terms" for information on usage and redistribution of * this file, and for a DISCLAIMER OF ALL WARRANTIES. * - * RCS: @(#) $Id: tclCompExpr.c,v 1.58 2007/07/05 18:31:52 dgp Exp $ + * RCS: @(#) $Id: tclCompExpr.c,v 1.59 2007/07/05 22:21:35 dgp Exp $ */ #include "tclInt.h" @@ -84,9 +84,36 @@ #define UNARY_PLUS ( UNARY | PLUS) #define UNARY_MINUS ( UNARY | MINUS) -#define FUNCTION ( UNARY | BAREWORD) -#define START ( UNARY | 4) -#define OPEN_PAREN ( UNARY | 5) +#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) @@ -94,7 +121,14 @@ #define BINARY_PLUS ( BINARY | PLUS) #define BINARY_MINUS ( BINARY | MINUS) -#define COMMA ( BINARY | 3) +#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) @@ -103,8 +137,16 @@ #define BIT_AND ( BINARY | 9) #define BIT_XOR ( BINARY | 10) #define BIT_OR ( BINARY | 11) -#define QUESTION ( BINARY | 12) -#define COLON ( BINARY | 13) +#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) @@ -115,11 +157,14 @@ #define OR ( BINARY | 21) #define STREQ ( BINARY | 22) #define STRNEQ ( BINARY | 23) -#define EXPON ( BINARY | 24) +#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) -#define END ( BINARY | 28) +#define CLOSE_PAREN ( BINARY | 27) /**/ +#define END ( BINARY | 28) /**/ /* * Integer codes indicating the form of an operand of an operator. |