Hello everyone— I have a random process that generates double cosets of the symmetric group. I would like to keep track of how often I have seen the various double cosets.
In hunting around, it seemed initially that dictionaries would be the perfect solution. I was able to use double cosets as keys, and checked in a few examples that it was doing the right thing. However, I have not been able to change the value of dictionaries, which is the way I was thinking about counting them. The documentation <http://www.gap-system.org/Manuals/doc/ref/chap28.html> says We hash by keys and also store a value. Keys cannot be removed from the > table, but the corresponding value can be changed. Fast access to last hash > index allows you to efficiently store more than one array of values –this > facility should be used with care. How does one change these values? I can’t find how to do that. If it matters, double cosets do not have an order in GAP4 and thus the Dictionary storage happens as a ListLookupDictionary, for which the Add method looks like: ############################################################################# ## #M AddDictionary(<dict>,<obj>,<val>) ## InstallOtherMethod(AddDictionary,"for lookup list dictionaries",true, [IsListLookupDictionary and IsMutable,IsObject,IsObject],0, function(d, x, val) x:=[Immutable(x),val]; # MakeImmutable(x); # to be able to store sortedness # We don't actually need to do that and we don't want to modify val # Add(d!.entries,x); end); Thank you! Erick -- Frederick "Erick" Matsen, Assistant Member Fred Hutchinson Cancer Research Center http://matsen.fredhutch.org/ _______________________________________________ Forum mailing list Forum@mail.gap-system.org http://mail.gap-system.org/mailman/listinfo/forum
