<div dir="ltr"><div><br></div><div>You mean</div><div><br></div><div>test() -></div><div> E = ets:new(test, [ordered_set]),</div><div> ets:insert(E, [{1,a},</div><div><span class="" style="white-space:pre"> </span> {22,b},</div>
<div><span class="" style="white-space:pre"> </span> {32,c},</div><div><span class="" style="white-space:pre"> </span> {47,d},</div><div><span class="" style="white-space:pre"> </span> {55,e},</div><div><span class="" style="white-space:pre"> </span> {97,f}]),</div>
<div> N = ets:next(E, 40),</div><div> P = ets:prev(E, 40),</div><div> {N,P}.</div><div><br></div><div>Seems to work - so to find the K nearest I just iterate prev and next keeping track of</div><div>which direction I have to move - very nice.</div>
<div><br></div><div>I had assumed that ets:next needed a pre-existing key in the table to perform a</div><div>next or prev operation.</div><div><br></div><div>Problem solved - very neatly</div><div><br></div><div>Thanks</div>
<div><br></div><div>/Joe</div><div><br></div><div><br></div><div><br></div><div><br></div></div><div class="gmail_extra"><br><br><div class="gmail_quote">On Tue, May 27, 2014 at 2:12 PM, Jesper Louis Andersen <span dir="ltr"><<a href="mailto:jesper.louis.andersen@gmail.com" target="_blank">jesper.louis.andersen@gmail.com</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="ltr">Use ets:next/1 and ets:prev/1 to expand a window from your target key. They work even if the initial key is not in the window. This should be fairly easy to implement for the 1d case. For higher-dimensional cases, k,d-trees is a favorite of mine.<div>
<br></div></div><div class="gmail_extra"><div><div class="h5"><br><br><div class="gmail_quote">On Tue, May 27, 2014 at 2:10 PM, Joe Armstrong <span dir="ltr"><<a href="mailto:erlang@gmail.com" target="_blank">erlang@gmail.com</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="ltr"><div class="gmail_extra"><br><br><div class="gmail_quote"><div>On Tue, May 27, 2014 at 1:26 PM, Tony Rogvall <span dir="ltr"><<a href="mailto:tony@rogvall.se" target="_blank">tony@rogvall.se</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div style="word-wrap:break-word">What about an ets ordered set table?</div></blockquote><div><br></div></div><div>How? - the problem is the key I lookup are not in the table</div>
<div><br></div><div>Suppose I insert keys</div><div><br></div><div> 1, 46, 218, 345, 578, 6541, 14671, ....</div><div><br></div><div>And I lookup a key 400 - this is not in the list - I'd like ets:nearest(400, Tab) to return </div>
<div>the key 354 entry - but there is no ets:nearest ...</div><span><font color="#888888"><div><br></div><div>/Joe</div></font></span><div><div><div><br></div><div> </div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<div style="word-wrap:break-word"><div><br></div><div>/Tony</div><div><br><div><div><div><div>On 27 maj 2014, at 12:58, Joe Armstrong <<a href="mailto:erlang@gmail.com" target="_blank">erlang@gmail.com</a>> wrote:</div>
<br></div></div><blockquote type="cite"><div><div><div dir="ltr"><div><br></div>What's the best data structure to support a "nearest key" operation?<br><br>I want a data structure that supports the following operations:<br>
<br> new() -> NewTree<br><br>
insert(Key, Value, Tree) -> NewTree<br> <br> delete(Key, Tree) -> NewTree<br> <br> nearest(Key, N, Tree) -> [{Key1,Val1},{Key2,Val2} ...].<br><br> Keys are 20 byte binaries, values are 6 byte binaries<div>
<br></div><div> The maximum number of keys of Key-Value pairs is 10 million.<br><br> nearest(Key, N, Tree) returns the N nearest items to Key in the tree<br><br> "near" means that the keys are near to each other. Often the key I want will not<br>
be in the tree, so I want nearby keys. The nearness measure is just the<br>"distance" between the two keys (ie the nearest N keys to the given key if the keys were to<br>be sorted)<br><br>Are there any Erlang libraries that do this?<br>
<br>/Joe<br></div></div></div></div><div>
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