Re: Curiosity of decimal numbers followed by concatenation

[KHMan <keinhong@...>]

Peter Cawley wrote:
> I was recently writing some syntax highlighting code for Lua, and
> while trying to duplicate the behaviour of the standard Lua parser, I
> noticed a curious behaviour. The first two of the following examples
> are completely normal. The third is unexpected to me - according the
> reference manual on numbers, "A numerical constant can be written with
> an optional decimal part and an optional decimal exponent", so I would
> expect it to be parsed like the first example, as the parser should
> stop trying to match a number at the second decimal point. The fourth
> example is included for completeness; it could in theory be parsed
> like the second example, or as 1. followed by . and ""
>
> > =1. ..""
> 1
> > =1 ..""
> 1
> > =1...""
> stdin:1: malformed number near '1...'
> > =1..""
> stdin:1: malformed number near '1..'
>
> Are there are reasons why the third example is parsed like it currently is?

In the interest of speed, there is no rewind (backtracking) in the 
llex.c. A number is preferentially parsed, so it cannot 
reinterpret the thing as something else, and it borks if a user 
pulls stunts like '1..""'. IMHO, borking on such snippets is good...

--
Cheers,
Kein-Hong Man (esq.)
Kuala Lumpur, Malaysia