Re: [HACKERS] Re: SQL compliance - why -- comments only at psql level?

On 2000-02-20, Tom Lane mentioned:

> select *-- 123
> ERROR: Can't find left op '*--' for type 23

> select /**/- 22
> ERROR: parser: parse error at or near ""

I believe that these things (certainly the first one) could be fixed by
making the {operator} rule in scan.l rescanning yytext for "--" or "/*"
(using string functions) and if found putting part of the token back in
the input stream using yyless().

> Meanwhile, psql is using some ad-hoc code to recognize comments,
> rather than a lexer, and it thinks both of these sequences are indeed
> comments.

Incidentally, it's right. ;)

> I suggest we change psql to not strip -- comments either.

That sounds reasonable, although we had a painful discussion about this
last fall, I recall, that ended with me leaving it like that. If someone
wants to bother, be my guest. One of these days, psql should get a lexer
to fix some other parsing problems as well.

> but <<EOF>> is a flex-ism not supported by regular lex.

Exclusive start conditions are not supported by regular lex either. We
lose. Sometimes I think we're actually doing people a favour by requiring
flex, because then they don't have to deal with incarnations like Sun's.

If you want to catch unbalanced quotes at the end of input, I could
imagine that some grand unified evilness via yywrap setting some global
flag or two might get the job done.

--
Peter Eisentraut Sernanders väg 10:115
peter_e(at)gmx(dot)net 75262 Uppsala
http://yi.org/peter-e/ Sweden