Re: re-search-backward bug

[Andreas Schwab <schwab@suse.de>]

Tom Wurgler <twurgler@goodyear.com> writes:

|> 1) Have a decimal number in a buffer, for example:
|> 
|> 1234.456
|> 
|> 2) Have your cursor BEFORE the number
|> 3) Do esc-x re-search-forward "[0-9]*\.[0-9]*"
|>    The complete number "1234.456" is found.
|> 4) Now have the cursor start AFTER the number
|> 5) Do esc-x re-search-backward "[0-9]*\.[0-9]*"
|>    It only matches back to the ".", specifically ".456"  
|> 
|> Why is going backward different than going forward?

Because matching by regexp is an inherently forward going operation.  It
is (conceptionally) implemented by going character by character until the
regexp matches.  That means that when going backwards the first match is
actually the _last_ match when viewed in the forward direction.

Andreas.

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Andreas Schwab, SuSE Labs, schwab@suse.de
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