On 2010.05.26., at 16:55, Rémi Forax wrote:
> Le 26/05/2010 16:26, Attila Szegedi a écrit :
>> Yeah, it's just that most software running under the term "parser generator"
>> today are in fact combined lexer/parser generators, and usually don't allow
>> for a situation where arbitrary new tokens can be introduced by the text
>> being analyzed (which is the case with both examples I gave). I was thinking
>> about this (Ruby parsing) some time ago and concluded that you'd most likely
>> end up with a hand-patched lexer, as I haven't seen this feature in any of
>> the ready-made solutions I know (there might be some that I don't know,
>> naturally).
>>
>> Attila.
>>
>
> For %Q{...}, the lexer lookup the matching right parenthesis, crop the text
> between the parenthesis
> and called another parser (or the same one at another start terminal) with
> the text.
Yeah, but my point is that you can use *any* character after Q to specify the
delimiter, i.e.:
%Qafooa
is equal to
"foo"
so your lexer must be ready to use as a terminating character whatever
character follows immediately after %Q. It's just that it'll have special cases
for some chars - most notably parentheses, brackets, and braces, so a string
starting with %Q{ will not be terminated by { but by }. Most people will use {
and }, but the point is that you are free to use *any* character.
Attila.
>
> Rémi
>
>> On 2010.05.26., at 16:02, John Cowan wrote:
>>
>>
>>> On Wed, May 26, 2010 at 7:35 AM, Attila Szegedi<[email protected]> wrote:
>>>
>>>> Out of professional curiosity: how do you implement
>>>> 1. Ruby's here docs
>>>> 2. Ruby's %Q, %q, %x and %r constructs
>>>> with any LL(k) or LALR parser generator's grammar language?
>>>>
>>> That's what lexers are for.
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