Re: Curiosity of decimal numbers followed by concatenation

[Vaughan McAlley <ockegheim@...>]

... is also vararg. With different meanings of . , .. and ... ,
judicious spaces prevent confusing both the parser and the reader.

Vaughan

On 5 February 2010 12:13, KHMan <keinhong@gmail.com> wrote:
> 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
>