Re: [Caml-list] a few lexing questions

[John Max Skaller <skaller@ozemail.com.au>]

Michal Moskal wrote:

> On Mon, Apr 28, 2003 at 02:13:48PM -0400, Alan Schmitt wrote:
> 
>>A second question is about integration this code with other lexing code
>>or streams. An iCalendar file cannot have a line that is longer than 75
>>bytes, excluding line break. A line may be broken anywhere as long as
>>there is a space at the beginning of the next line, as in:
>>
>>this is a very lo
>> ng line
>>
>>represents "this is a very long line". As this break may occur anywhere
>>(even inside keywords), I assume when writing the lexer these kind of
>>lines have been already merged together. I know how to implement the
>>merging using a temp file, but I'm looking for a nicer solution (like
>>using a stream, or using one lexer to feed the current lexer). Any
>>suggestion ?
>>
> 
> Maybe Lexing.from_function ? 


Yes, I do this. In the lexer:

....
| "(" { fun state -> state#inbody; [LPAR (state#get_srcref lexbuf)] }
....

Notice each executable section is a function accepting
the state object. You can form a closure of a method
of a lexer state class and pass that to Lexing.from_function,
and you call the lexer function with an extra arguemnt like:

lex_my_stuff lexbuf state


In that way you can

(a) pre-process the input
(b) maintain state such as the original line number


-- 
John Max Skaller, mailto:skaller@ozemail.com.au
snail:10/1 Toxteth Rd, Glebe, NSW 2037, Australia.
voice:61-2-9660-0850


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