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match using the standard algorithm, you have to do kludgy things with 
match using the standard algorithm, you have to do kludgy things with 
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callouts. 
callouts. 
146 
.P 
.P 
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2. There is much better support for partial matching. The restrictions on the 
2. Because the alternative algorithm scans the subject string just once, and 

content of the pattern that apply when using the standard algorithm for partial 


matching do not apply to the alternative algorithm. For nonanchored patterns, 


the starting position of a partial match is available. 


.P 


3. Because the alternative algorithm scans the subject string just once, and 

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never needs to backtrack, it is possible to pass very long subject strings to 
never needs to backtrack, it is possible to pass very long subject strings to 
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the matching function in several pieces, checking for partial matching each 
the matching function in several pieces, checking for partial matching each 
150 
time. 
time. 
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.rs 
.rs 
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.sp 
.sp 
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.nf 
.nf 
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Last updated: 19 April 2008 
Last updated: 25 August 2009 
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Copyright (c) 19972008 University of Cambridge. 
Copyright (c) 19972009 University of Cambridge. 
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.fi 
.fi 