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unput() messes up yy_at_bol

To: Xinying Li <>
Subject: Re: FLEX ?
In-reply-to: Your message of Wed, 13 Nov 1996 17:28:38 PST.
Date: Wed, 13 Nov 1996 19:51:54 PST
From: Vern Paxson <vern>

> "unput()" them to input flow, question occurs. If I do this after I scan
> a carriage, the variable "YY_CURRENT_BUFFER->yy_at_bol" is changed. That
> means the carriage flag has gone.

You can control this by calling yy_set_bol().  It's described in the manual.

>      And if in pre-reading it goes to the end of file, is anything done
> to control the end of curren buffer and end of file?

No, there's no way to put back an end-of-file.

>      By the way I am using flex 2.5.2 and using the "-l".

The latest release is 2.5.4, by the way.  It fixes some bugs in 2.5.2 and
2.5.3.  You can get it from