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Ensure map size does not grow too much
Posted: 21 Jun 2016 18:19
by houdinix64
hi.any idea how to solve this, to prevent the map size not too grow to much.I wanted my mapsize to contain only 10pairs of key/value and my priority is to remove the old values first. adv thanks.
Re: Ensure map size does not grow too much
Posted: 21 Jun 2016 18:43
by Bushmills
What you're looking for is essentially a circular buffer - those are easier to implement with lists, as indexed addressing is possible with those - but they don't provide the hashed addressing offered by maps. Is the key to value lookup important to you?
Re: Ensure map size does not grow too much
Posted: 21 Jun 2016 19:07
by houdinix64
The map contains contact name and numbers and from time to time it grows.So that i want it to maintain it to 10-20 only. Im creating a flow that when i access and view the map using Input dialog, it will show only the 10 most recent contact names..
Im sorry i cant explain it clearly and also for bad english.
Re: Ensure map size does not grow too much
Posted: 21 Jun 2016 19:33
by Bushmills
A map has no concept of "recent" or chronological sequence of additions. Only thing I can currently think of is an additional list, used to keep map keys, index addressed, with a wrap around index. Before a list item gets reused (overwritten), it is read, and the corresponding map element removed.
Maybe there's a better solution somebody else can think of, or I get another idea. What I do in similar cases is appending to file, and display tail -n lines from that file - but whether you could imagine replacing hashed map lookup against a grep on that file is something I don't know.
Re: Ensure map size does not grow too much
Posted: 21 Jun 2016 19:45
by houdinix64
Thanks..
I got the idea from this flow made by Martin. I want to tweak it to create other flow but map will grow for sure.
Sorry i dont know how to post that topic. Search "send sms by timeframe"
http://automagic4android.com/flow.php?i ... 151bf39282
Re: Ensure map size does not grow too much
Posted: 21 Jun 2016 20:13
by Martin
The maps used by Automagic keep the iteration order of elements (insertion order) since it's often easier to understand and debug a map when the entries are not ordered "randomly".
However, re-inserting an element does not affect the order:
Code: Select all
map = newMap();
addMapEntry(map, "a", 1);
addMapEntry(map, "b", 2);
addMapEntry(map, "c", 3);
addMapEntry(map, "a", 4);
The map will contain following entries:
a->4
b->2
c->3
When you overwrite entries, you could change your script to always remove the entry first and then insert the entry to the map:
Code: Select all
map = newMap();
addMapEntry(map, "a", 1);
addMapEntry(map, "b", 2);
addMapEntry(map, "c", 3);
removeMapEntry(map, "a");
addMapEntry(map, "a", 4);
which yields:
b->2
c->3
a->4
You could use this special behavior to remove the first (oldest) element from the map:
Code: Select all
if (length(map) > 10)
{
firstKey = getMapKeys(map)[0];
removeMapEntry(map, firstKey);
}
