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Full Discussion: Hash Function Speed
Top Forums Programming Hash Function Speed Post 302364275 by Corona688 on Thursday 22nd of October 2009 01:01:49 PM
Old 10-22-2009
Quote:
Originally Posted by jim mcnamara
OP's additive hash fails to treat permutations, i.e., “xyz”, “zyx”, and “xzy” all result in the same hash value.
Once again, sorry, but look closer: It's not an additive hash. Order alters the value because it multiplies hashval by 37 each iteration before adding the next character. With a table size of 2048, it gives me:
Code:
hash("xyz") == 943
hash("zyx") == 1631
hash("xzy") == 979

 

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Tie::Hash::NamedCapture(3pm)				 Perl Programmers Reference Guide			      Tie::Hash::NamedCapture(3pm)

NAME
Tie::Hash::NamedCapture - Named regexp capture buffers SYNOPSIS
tie my %hash, "Tie::Hash::NamedCapture"; # %hash now behaves like %+ tie my %hash, "Tie::Hash::NamedCapture", all => 1; # %hash now access buffers from regexp in $qr like %- DESCRIPTION
This module is used to implement the special hashes "%+" and "%-", but it can be used to tie other variables as you choose. When the "all" parameter is provided, then the tied hash elements will be array refs listing the contents of each capture buffer whose name is the same as the associated hash key. If none of these buffers were involved in the match, the contents of that array ref will be as many "undef" values as there are capture buffers with that name. In other words, the tied hash will behave as "%-". When the "all" parameter is omitted or false, then the tied hash elements will be the contents of the leftmost defined buffer with the name of the associated hash key. In other words, the tied hash will behave as "%+". The keys of "%-"-like hashes correspond to all buffer names found in the regular expression; the keys of "%+"-like hashes list only the names of buffers that have captured (and that are thus associated to defined values). SEE ALSO
perlreapi, re, "Pragmatic Modules" in perlmodlib, "%+" in perlvar, "%-" in perlvar. perl v5.16.3 2013-03-04 Tie::Hash::NamedCapture(3pm)
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