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Re: variable length fields
From: |
Hans Aberg |
Subject: |
Re: variable length fields |
Date: |
Thu, 06 Jan 2005 19:27:45 +0100 |
User-agent: |
Microsoft-Outlook-Express-Macintosh-Edition/5.0.6 |
At 12:34 +0000 2005/01/06, Leo Kirch wrote:
>i've got the following problem with bison: imagine a text file by the
>structure of one line that tells us how many lines will follow and the
>following lines... ahm... sample:
>
> ......
> ......
> 3 // three lines will follow
> line1 // the first line...
> line2
> line3 //the last line..
> 2
> anotherline1
> anotherline2
> ....
> ...
>
>and so on. but how do i tell bison to remember (3) and then read exactly the
>next three lines?
It might be easiest to check this semantically, in the actions.
%{
size_t line_count, maxline_count;
%}
%token NUMBER
%%
get_lines:
NUMBER { maxline_count = $1 } lines
;
lines:
{ line_count = 0; }
| lines line { (++line_count > maxline_count) error ... }
;
Hans Aberg