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Modify lexing of multi-char operators per pghackers discussion around

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16-Mar-00: trailing + or - is not part of the operator unless the operator
also contains characters not present in SQL92-defined operators.  This
solves the 'X=-Y' problem without unduly constraining users' choice of
operator names --- in particular, no existing Postgres operator names
become invalid.

Also, remove processing of // comments, as agreed in the same thread.
This commit is contained in:
Tom Lane
2000-03-18 18:03:12 +00:00
parent 2b23e86447
commit f945f46193
5 changed files with 211 additions and 81 deletions
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80
src/backend/parser/scan.l
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@@ -9,7 +9,7 @@
*
*
* IDENTIFICATION
* $Header: /cvsroot/pgsql/src/backend/parser/scan.l,v 1.67 2000/03/13 01:52:06 tgl Exp $
* $Header: /cvsroot/pgsql/src/backend/parser/scan.l,v 1.68 2000/03/18 18:03:09 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -87,10 +87,10 @@ static void addlit(char *ytext, int yleng);
* and to eliminate parsing troubles for numeric strings.
* Exclusive states:
* <xb> binary numeric string - thomas 1997-11-16
* <xc> extended C-style comments - tgl 1997-07-12
* <xd> delimited identifiers (double-quoted identifiers) - tgl 1997-10-27
* <xc> extended C-style comments - thomas 1997-07-12
* <xd> delimited identifiers (double-quoted identifiers) - thomas 1997-10-27
* <xh> hexadecimal numeric string - thomas 1997-11-16
* <xq> quoted strings - tgl 1997-07-30
* <xq> quoted strings - thomas 1997-07-30
*/
%x xb
@@ -144,7 +144,7 @@ xdinside [^"]+
* have something like plus-slash-star, lex will think this is a 3-character
* operator whereas we want to see it as a + operator and a comment start.
* The solution is two-fold:
* 1. append {op_and_self}* to xcstart so that it matches as much text as
* 1. append {op_chars}* to xcstart so that it matches as much text as
* {operator} would. Then the tie-breaker (first matching rule of same
* length) ensures xcstart wins. We put back the extra stuff with yyless()
* in case it contains a star-slash that should terminate the comment.
@@ -154,7 +154,7 @@ xdinside [^"]+
* SQL92-style comments, which start with dash-dash, have similar interactions
* with the operator rule.
*/
xcstart \/\*{op_and_self}*
xcstart \/\*{op_chars}*
xcstop \*+\/
xcinside ([^*]+)|(\*+[^/])
@@ -166,10 +166,19 @@ identifier {letter}{letter_or_digit}*
typecast "::"
/* NB: if you change "self", fix the copy in the operator rule too! */
/*
* "self" is the set of chars that should be returned as single-character
* tokens. "op_chars" is the set of chars that can make up "Op" tokens,
* which can be one or more characters long (but if a single-char token
* appears in the "self" set, it is not to be returned as an Op). Note
* that the sets overlap, but each has some chars that are not in the other.
*
* If you change either set, adjust the character lists appearing in the
* rule for "operator"!
*/
self [,()\[\].;$\:\+\-\*\/\%\^\<\>\=\|]
op_and_self [\~\!\@\#\^\&\|\`\?\$\:\+\-\*\/\%\<\>\=]
operator {op_and_self}+
op_chars [\~\!\@\#\^\&\|\`\?\$\:\+\-\*\/\%\<\>\=]
operator {op_chars}+
/* we no longer allow unary minus in numbers.
* instead we pass it separately to parser. there it gets
@@ -202,7 +211,7 @@ horiz_space [ \t\f]
newline [\n\r]
non_newline [^\n\r]
comment (("--"|"//"){non_newline}*)
comment ("--"{non_newline}*)
whitespace ({space}|{comment})
@@ -220,7 +229,7 @@ other .
/* DO NOT PUT ANY COMMENTS IN THE FOLLOWING SECTION.
* AT&T lex does not properly handle C-style comments in this second lex block.
* So, put comments here. tgl - 1997-09-08
* So, put comments here. thomas - 1997-09-08
*
* Quoted strings must allow some special characters such as single-quote
* and newline.
@@ -329,23 +338,57 @@ other .
{self} { return yytext[0]; }
{operator} {
/* Check for embedded slash-star or dash-dash */
char *slashstar = strstr((char*)yytext, "/*");
char *dashdash = strstr((char*)yytext, "--");
/*
* Check for embedded slash-star or dash-dash; those
* are comment starts, so operator must stop there.
* Note that slash-star or dash-dash at the first
* character will match a prior rule, not this one.
*/
int nchars = yyleng;
char *slashstar = strstr((char*)yytext, "/*");
char *dashdash = strstr((char*)yytext, "--");
if (slashstar && dashdash)
{
/* if both appear, take the first one */
if (slashstar > dashdash)
slashstar = dashdash;
}
else if (!slashstar)
slashstar = dashdash;
if (slashstar)
nchars = slashstar - ((char*)yytext);
/*
* For SQL92 compatibility, '+' and '-' cannot be the
* last char of a multi-char operator unless the operator
* contains chars that are not in SQL92 operators.
* The idea is to lex '=-' as two operators, but not
* to forbid operator names like '?-' that could not be
* sequences of SQL92 operators.
*/
while (nchars > 1 &&
(yytext[nchars-1] == '+' ||
yytext[nchars-1] == '-'))
{
int nchars = slashstar - ((char*)yytext);
int ic;
for (ic = nchars-2; ic >= 0; ic--)
{
if (strchr("~!@#&`?$:%^|", yytext[ic]))
break;
}
if (ic >= 0)
break; /* found a char that makes it OK */
nchars--; /* else remove the +/-, and check again */
}
if (nchars < yyleng)
{
/* Strip the unwanted chars from the token */
yyless(nchars);
/* If what we have left is only one char, and it's
/*
* If what we have left is only one char, and it's
* one of the characters matching "self", then
* return it as a character token the same way
* that the "self" rule would have.
@@ -355,8 +398,9 @@ other .
return yytext[0];
}
/* Convert "!=" operator to "<>" for compatibility */
if (strcmp((char*)yytext, "!=") == 0)
yylval.str = pstrdup("<>"); /* compatibility */
yylval.str = pstrdup("<>");
else
yylval.str = pstrdup((char*)yytext);
return Op;