Re: [Help-source-highlight] regexp for scheme blocks in lilypond language

[Lorenzo Bettini]

On 01/22/2012 12:20 PM, Federico Bruni wrote:
> Il 21/01/2012 15:24, Lorenzo Bettini ha scritto:
> > > Thanks, this should be the direction, but it's not so easy.
> > > First, the doc says:
> > >
> > > "Note that, in order for a delimited language element to be nested, its
> > > starting and ending elements must be different"
> > >
> > > I may be wrong, but I would add: they also have to be specular.
> > > In my case delimiters are not specular.
> >
> > no, that's not requested :)
> > note that end delimiter may refer to start delimiter (using the regex
> > syntax for referring the matched part of another expression); this is
> > the case for lua.lang where nested comments can have different syntax
> > and the delimiter has to match the starting delimiter and refers to it
> > (with this respect, source-highlight is pretty powerful, but I may be
> > biased ;)
>
> thanks, but I'm still far away from understanding
>
> can you give me some pointer/keyword which can help me understanding the
> following regexp (in particular, I can't understand (=*) and @{1})?
>
> environment comment delim `--\[(=*)\[` "]" + @{1} + "]" multiline nested
> begin
> include "url.lang"
> environment comment delim "[[" "]]" multiline nested begin
> include "url.lang"
> end
> end

it says that the starting delimiter is

`--\[(=*)\[`

while the end delimiter is

"]" + @{1} + "]"

(please have a look at the documentation to understand the difference 
among ", ', ` )

the starting delimiter searches for elements of the shape

--[[, --[=[, --[==[

etc. ( (=*) is just a regular expression that matches any multiple 
occurrence of =, even none)

the end delimiter uses the feature I was talking about

"]" + @{1} + "]"

in particular @{1} refers to the first grouped matched string of the 
start delimiter, i.e., in this example (=*)  (as I said, take a look at 
the implementation concerning ` ` which keeps grouped regular expressions).

This means that if the starting delimiter matched --[[ then the end 
delimiter will try to match ]] ; if the starting delimiter matched --[=[ 
then the end delimiter will try to match ]=] ; if the starting delimiter 
matched --[==[ then the end delimiter will try to match ]==] ; and so on...

pretty powerful, isn't it? O:)

The inner

environment comment delim "[[" "]]" multiline nested begin
        include "url.lang"
  end

will try to match only comments [[ ]] because, if I remember correctly, 
in Lua inside a comment --[[ ]] you can only have [[ ]] comments...

is that clearer now?

cheers
        Lorenzo

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Lorenzo Bettini, PhD in Computer Science, DI, Univ. Torino
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