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authordgp <dgp@users.sourceforge.net>2007-07-10 21:37:43 (GMT)
committerdgp <dgp@users.sourceforge.net>2007-07-10 21:37:43 (GMT)
commitf010370ffaaa227e9f89fe613d832a2c36b5f648 (patch)
tree0386d7db171731ff9222b01b6e84edd076d86e99
parentfc6c2be72980d34595e2761eb586e783ac20efd2 (diff)
downloadtcl-f010370ffaaa227e9f89fe613d832a2c36b5f648.zip
tcl-f010370ffaaa227e9f89fe613d832a2c36b5f648.tar.gz
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Renamed some variables for
clarity and replaced some cryptic logic with more readable macros.
-rw-r--r--ChangeLog3
-rw-r--r--generic/tclCompExpr.c161
2 files changed, 117 insertions, 47 deletions
diff --git a/ChangeLog b/ChangeLog
index c9a8448..0f96c5c 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -6,7 +6,8 @@
issues anyway. Also, converted precedence definitions and lookup
tables to use symbolic constants instead of raw number for improved
readability, and continued extending/improving/correcting comments.
- Removed some unused counter variables.
+ Removed some unused counter variables. Renamed some variables for
+ clarity and replaced some cryptic logic with more readable macros.
2007-07-09 Don Porter <dgp@users.sourceforge.net>
diff --git a/generic/tclCompExpr.c b/generic/tclCompExpr.c
index bb5fc32..f601427 100644
--- a/generic/tclCompExpr.c
+++ b/generic/tclCompExpr.c
@@ -12,7 +12,7 @@
* 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 1.64 2007/07/10 17:07:37 dgp Exp $
+ * RCS: @(#) $Id: tclCompExpr.c,v 1.65 2007/07/10 21:37:44 dgp Exp $
*/
#include "tclInt.h"
@@ -69,6 +69,15 @@ enum OperandTypes {
};
/*
+ * Readable macros to test whether a "pointer" value points to an operator.
+ * They operate on the "non-negative integer -> operator; negative integer ->
+ * a non-operator OperandType" distinction.
+ */
+
+#define IsOperator(l) ((l) >= 0)
+#define NotOperator(l) ((l) < 0)
+
+/*
* Note that it is sufficient to store in the tree just the type of leaf
* operand, without any explicit pointer to which leaf. This is true because
* the inorder traversals of the completed tree we perform are known to visit
@@ -453,13 +462,16 @@ ParseExpr(
unsigned char lexeme = START; /* Most recent lexeme parsed. */
int lastOpen = 0; /* Index of the OpNode of the OPEN_PAREN
* operator we most recently matched. */
- int lastWas = 0; /* Stores what the lexeme parsed the
- * previous pass through the parsing loop
- * was. If it was an operator, lastWas is
+ int lastParsed = 0; /* Stores info about what the lexeme parsed
+ * the previous pass through the parsing loop
+ * was. If it was an operator, lastParsed is
* the index of the OpNode for that operator.
- * If it was not and operator, lastWas holds
+ * If it was not and operator, lastParsed holds
* an OperandTypes value encoding what we
- * need to know about it. */
+ * need to know about it. The initial value
+ * is 0 indicating that as we start the "last
+ * thing we parsed" was the START lexeme stored
+ * in node 0. */
/* These variables control generation of the error message. */
Tcl_Obj *msg = NULL; /* The error message. */
@@ -505,14 +517,21 @@ ParseExpr(
}
while ((code == TCL_OK) && (lexeme != END)) {
- OpNode *nodePtr;
- Tcl_Token *tokenPtr = NULL;
- Tcl_Obj *literal = NULL;
+ OpNode *nodePtr; /* Points to the OpNode we may fill this
+ * pass through the loop. */
+ Tcl_Obj *literal; /* Filled by the ParseLexeme() call when
+ * a literal is parsed that has a Tcl_Obj
+ * rep worth preserving. */
const char *lastStart = start - scanned;
+ /* Compute where the lexeme parsed the
+ * previous pass through the loop began.
+ * This is helpful for detecting invalid
+ * octals and providing more complete error
+ * messages. */
/*
- * Each pass through this loop adds one more OpNode. Allocate space
- * for one if required.
+ * Each pass through this loop adds up to one more OpNode. Allocate
+ * space for one if required.
*/
if (nodesUsed >= nodesAvailable) {
@@ -607,20 +626,33 @@ ParseExpr(
break;
case PLUS:
case MINUS:
- if (lastWas < 0) {
- lexeme |= BINARY;
- } else {
+ if (IsOperator(lastParsed)) {
+ /*
+ * A "+" or "-" coming just after another operator
+ * must be interpreted as a unary operator.
+ */
lexeme |= UNARY;
+ } else {
+ lexeme |= BINARY;
}
}
}
/*
- * Add node to parse tree based on category.
+ * Handle lexeme based on its category.
*/
switch (NODE_TYPE & lexeme) {
+
+ /*
+ * Each LEAF results in either a literal getting appended to the
+ * litList, or a sequence of Tcl_Tokens representing a Tcl word
+ * getting appended to the parsePtr->tokens. No OpNode is filled
+ * for this lexeme.
+ */
+
case LEAF: {
+ Tcl_Token *tokenPtr;
const char *end;
int wordIndex;
@@ -639,7 +671,7 @@ ParseExpr(
break;
}
- if (lastWas < 0) {
+ if (NotOperator(lastParsed)) {
msg = Tcl_ObjPrintf("missing operator at %s", mark);
if (lastStart[0] == '0') {
Tcl_Obj *copy = Tcl_NewStringObj(lastStart,
@@ -660,7 +692,7 @@ ParseExpr(
switch (lexeme) {
case NUMBER:
case BOOLEAN:
- lastWas = OT_LITERAL;
+ lastParsed = OT_LITERAL;
start += scanned;
numBytes -= scanned;
continue;
@@ -669,7 +701,8 @@ ParseExpr(
}
/*
- * Make room for at least 2 more tokens.
+ * Remaining LEAF cases may involve filling Tcl_Tokens, so
+ * make room for at least 2 more tokens.
*/
if (parsePtr->numTokens+1 >= parsePtr->tokensAvailable) {
@@ -686,6 +719,9 @@ ParseExpr(
code = Tcl_ParseQuotedString(interp, start, numBytes,
parsePtr, 1, &end);
if (code != TCL_OK) {
+ /* TODO: This adjustment of scanned is untested and
+ * and uncommented. Correct that. Its only possible
+ * purpose is to influence the error message. */
scanned = parsePtr->term - start;
scanned += (scanned < numBytes);
continue;
@@ -705,6 +741,9 @@ ParseExpr(
case VARIABLE:
code = Tcl_ParseVarName(interp, start, numBytes, parsePtr, 1);
if (code != TCL_OK) {
+ /* TODO: This adjustment of scanned is untested and
+ * and uncommented. Correct that. Its only possible
+ * purpose is to influence the error message. */
scanned = parsePtr->term - start;
scanned += (scanned < numBytes);
continue;
@@ -758,6 +797,9 @@ ParseExpr(
end = start;
start = tokenPtr->start;
if (code != TCL_OK) {
+ /* TODO: This adjustment of scanned is untested and
+ * and uncommented. Correct that. Its only possible
+ * purpose is to influence the error message. */
scanned = parsePtr->term - start;
scanned += (scanned < numBytes);
continue;
@@ -773,31 +815,55 @@ ParseExpr(
tokenPtr->size = scanned;
tokenPtr->numComponents = parsePtr->numTokens - wordIndex - 1;
if ((lexeme == QUOTED) || (lexeme == BRACED)) {
+
+ /*
+ * When a braced or quoted word within an expression
+ * is simple enough, we can store it as a literal rather
+ * than in its tokenized form. This is an advantage since
+ * the compiled bytecode is going to need the argument in
+ * Tcl_Obj form eventually, so it's to our advantage to just
+ * get there now, and avoid the need to convert from Tcl_Token
+ * form again later. Currently we only store literals
+ * for things parsed as single TEXT tokens (known as
+ * TCL_TOKEN_SIMPLE_WORD in other contexts). In this
+ * simple case, the literal string we store is identical
+ * to a substring of the original expression.
+ *
+ * TODO: We ought to be able to store as a literal any
+ * word which is known at compile-time, including those that
+ * contain backslash substitution. This can be helpful to
+ * store multi-line strings that include escaped newlines,
+ * or strings that include multi-byte characters expressed
+ * in \uHHHH form. Removing the first two tests here is
+ * sufficient to make that change, but will lead to a
+ * Tcl_Panic() in GenerateTokensForLiteral() until that routine
+ * is revised to handle such literals.
+ */
+
literal = Tcl_NewObj();
- /* TODO: allow all compile-time known words */
if (tokenPtr->numComponents == 1
&& tokenPtr[1].type == TCL_TOKEN_TEXT
&& TclWordKnownAtCompileTime(tokenPtr, literal)) {
Tcl_ListObjAppendElement(NULL, litList, literal);
- lastWas = OT_LITERAL;
+ lastParsed = OT_LITERAL;
parsePtr->numTokens = wordIndex;
break;
}
Tcl_DecrRefCount(literal);
}
- lastWas = OT_TOKENS;
+ lastParsed = OT_TOKENS;
break;
}
case UNARY:
- if (lastWas < 0) {
+ if (NotOperator(lastParsed)) {
msg = Tcl_ObjPrintf("missing operator at %s", mark);
scanned = 0;
insertMark = 1;
code = TCL_ERROR;
continue;
}
- lastWas = nodesUsed;
+ lastParsed = nodesUsed;
nodePtr->lexeme = lexeme;
nodePtr->precedence = prec[lexeme];
nodePtr->left = OT_NONE;
@@ -810,7 +876,7 @@ ParseExpr(
OpNode *otherPtr = NULL;
unsigned char precedence = prec[lexeme];
- if (lastWas >= 0) {
+ if (IsOperator(lastParsed)) {
if ((lexeme == CLOSE_PAREN)
&& (nodePtr[-1].lexeme == OPEN_PAREN)) {
if (nodePtr[-2].lexeme == FUNCTION) {
@@ -820,7 +886,7 @@ ParseExpr(
*/
scanned = 0;
- lastWas = OT_EMPTY;
+ lastParsed = OT_EMPTY;
nodePtr[-1].left--;
break;
}
@@ -864,16 +930,16 @@ ParseExpr(
continue;
}
- if (lastWas == OT_NONE) {
+ if (lastParsed == OT_NONE) {
otherPtr = nodes + lastOpen - 1;
- lastWas = lastOpen;
+ lastParsed = lastOpen;
} else {
otherPtr = nodePtr - 1;
}
while (1) {
/*
- * lastWas is "index" of item to be linked. otherPtr points to
- * competing operator.
+ * lastParsed is "index" of item to be linked.
+ * otherPtr points to competing operator.
*/
if (otherPtr->precedence < precedence) {
@@ -895,8 +961,9 @@ ParseExpr(
* must be linked up in sensible pairs.
*/
- if ((otherPtr->lexeme == QUESTION) && ((lastWas < 0)
- || (nodes[lastWas].lexeme != COLON))) {
+ if ((otherPtr->lexeme == QUESTION)
+ && (NotOperator(lastParsed)
+ || (nodes[lastParsed].lexeme != COLON))) {
break;
}
if ((otherPtr->lexeme == COLON) && (lexeme == QUESTION)) {
@@ -905,7 +972,7 @@ ParseExpr(
}
/*
- * We should link the lastWas item to the otherPtr as its
+ * We should link the lastParsed item to the otherPtr as its
* right operand. First make some syntax checks.
*/
@@ -916,8 +983,9 @@ ParseExpr(
code = TCL_ERROR;
break;
}
- if ((otherPtr->lexeme == QUESTION) && ((lastWas < 0)
- || (nodes[lastWas].lexeme != COLON))) {
+ if ((otherPtr->lexeme == QUESTION)
+ && (NotOperator(lastParsed)
+ || (nodes[lastParsed].lexeme != COLON))) {
msg = Tcl_ObjPrintf(
"missing operator \":\" at %s", mark);
scanned = 0;
@@ -925,7 +993,8 @@ ParseExpr(
code = TCL_ERROR;
break;
}
- if ((lastWas >= 0) && (nodes[lastWas].lexeme == COLON)
+ if (IsOperator(lastParsed)
+ && (nodes[lastParsed].lexeme == COLON)
&& (otherPtr->lexeme != QUESTION)) {
TclNewLiteralStringObj(msg,
"unexpected operator \":\" without preceding \"?\"");
@@ -937,11 +1006,11 @@ ParseExpr(
* Link orphan as right operand of otherPtr.
*/
- otherPtr->right = lastWas;
- if (lastWas >= 0) {
- nodes[lastWas].parent = otherPtr - nodes;
+ otherPtr->right = lastParsed;
+ if (lastParsed >= 0) {
+ nodes[lastParsed].parent = otherPtr - nodes;
}
- lastWas = otherPtr - nodes;
+ lastParsed = otherPtr - nodes;
if (otherPtr->lexeme == OPEN_PAREN) {
/*
@@ -969,7 +1038,7 @@ ParseExpr(
code = TCL_ERROR;
continue;
}
- lastWas = OT_NONE;
+ lastParsed = OT_NONE;
lastOpen = otherPtr - nodes;
otherPtr->left++;
@@ -989,7 +1058,7 @@ ParseExpr(
}
otherPtr->left++;
}
- if ((lastWas >= 0) && (nodes[lastWas].lexeme == COLON)) {
+ if (IsOperator(lastParsed) && (nodes[lastParsed].lexeme == COLON)) {
TclNewLiteralStringObj(msg,
"unexpected operator \":\" without preceding \"?\"");
code = TCL_ERROR;
@@ -1006,14 +1075,14 @@ ParseExpr(
nodePtr->lexeme = lexeme;
nodePtr->precedence = precedence;
nodePtr->right = -1;
- nodePtr->left = lastWas;
- if (lastWas < 0) {
+ nodePtr->left = lastParsed;
+ if (lastParsed < 0) {
nodePtr->parent = nodePtr - nodes - 1;
} else {
- nodePtr->parent = nodes[lastWas].parent;
- nodes[lastWas].parent = nodePtr - nodes;
+ nodePtr->parent = nodes[lastParsed].parent;
+ nodes[lastParsed].parent = nodePtr - nodes;
}
- lastWas = nodesUsed;
+ lastParsed = nodesUsed;
nodesUsed++;
break;
}