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<div dir="ltr" data-setdir="false"><div><div dir="ltr" style="font-family: Helvetica Neue, Helvetica, Arial, sans-serif; font-size: 16px;">I did not check the code for 'case ... of ...' constuction in GHC, my intention comes from the explanations how this construction works in Haskell in some teaching materials.</div><div dir="ltr" style="font-family: Helvetica Neue, Helvetica, Arial, sans-serif; font-size: 16px;">So, definitely I should do more exploratory work. Nevertheless, the type signatures and sorting is realized for rather general situation and can be therefore preferable for some situations.</div><div dir="ltr" style="font-family: Helvetica Neue, Helvetica, Arial, sans-serif; font-size: 16px;"><br clear="none"></div><div dir="ltr" style="font-family: Helvetica Neue, Helvetica, Arial, sans-serif; font-size: 16px;">Best regards,</div><div dir="ltr" style="font-family: Helvetica Neue, Helvetica, Arial, sans-serif; font-size: 16px;">Oleksandr Zhabenko.</div></div><br></div><div><br></div>
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субота, 21 вересня 2019 р., 21:07:25 GMT+2, Олександр Жабенко <olexandr576@yahoo.com> написав:
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<div dir="ltr">I did not check the code for 'case ... of ...' constuction in GHC, my intention comes from the explanations how this construction works in Haskell in some teaching materials.</div><div dir="ltr">So, definitely I should do more exploratory work. Nevertheless, the type signatures and sorting is realized for rather general situation and can be therefore preferable for some situations.</div><div dir="ltr"><br clear="none"></div><div dir="ltr">Best regards,</div><div dir="ltr">Oleksandr Zhabenko.</div><div dir="ltr"><br clear="none"></div>
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субота, 21 вересня 2019 р., 20:59:03 GMT+2, olexandr543@yahoo.com <olexandr543@yahoo.com> написав:
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<div>Yes, you can use IntMap. It needs another dependency and the complexity choice as <i>O(log (min (n, W)))</i> where W is a number of bits in a representing key, used for mapping. <br clear="none"></div><div dir="ltr"><div><div dir="ltr">For me, it is rather hard to solve whether it can be better, because it raises another problem of efficient binary representation of the keys.</div><div dir="ltr"><br clear="none"></div><div dir="ltr">While working on the topic, I found out that may be the most efficient will be hashing (for lookup it can be used e. g. Cuckoo hashing) and there is a library in Haskell for it.</div><div dir="ltr"><a rel="nofollow" shape="rect" class="yiv1401277158ydp7eec1b35yiv1322360768enhancr_card_9728930781" target="_blank" href="http://hackage.haskell.org/package/hashtables-1.2.3.4/docs/Data-HashTable-IO.html" style="color:rgb(25, 106, 212);text-decoration-line:underline;">Data.HashTable.IO</a> </div><div dir="ltr">Using it, you can write something like:</div><div dir="ltr"><br clear="none"></div><div dir="ltr"><div style="font-family:Helvetica Neue, Helvetica, Arial, sans-serif;font-size:16px;"><div>{-# LANGUAGE ScopedTypeVariables #-}</div><div><br clear="none"></div><div>module Main where</div><div><br clear="none"></div><div>import qualified Data.HashTable.IO as I<br clear="none"></div><div>import Data.Maybe (fromJust,isJust)<br clear="none"></div><div>import System.Environment (getArgs)</div><div><br clear="none"></div><div>main :: IO ()<br clear="none"></div><div>main = do </div><div> args <- getArgs</div><div> let a = [([z,t],x) | x <- ['a'..'d'], z <- ['f'..'t'], t <- ['a'..'p'], [x,z,t] <= "fnf"] </div><div> b :: I.CuckooHashTable String Char <- I.fromList a </div><div> c <- I.lookup b ("kn") </div><div> let d1 u = do </div><div> d <- I.lookup b u</div><div> print c</div><div> if isJust d </div><div> then putStrLn . show . fromJust $ d </div><div> else putStrLn "Nothing"</div><div> return () </div><div> if null args </div><div> then d1 "fa"</div><div> else d1 (head $ args)</div></div><br clear="none" style="font-family:Helvetica Neue, Helvetica, Arial, sans-serif;font-size:16px;"><div style="font-family:Helvetica Neue, Helvetica, Arial, sans-serif;font-size:16px;"><br clear="none"></div><div class="yiv1401277158ydp7eec1b35yiv1322360768ydp5578d2f1yahoo-link-enhancr-card yiv1401277158ydp7eec1b35yiv1322360768ydp5578d2f1yahoo-link-enhancr-not-allow-cover yiv1401277158ydp7eec1b35yiv1322360768ydp5578d2f1ymail-preserve-class 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42);">Data.HashTable.IO</h2><p class="yiv1401277158ydp7eec1b35yiv1322360768ydp5578d2f1card-description" style="font-size:12px;line-height:16px;margin:0px;color:rgb(151, 155, 167);"></p></td></tr></tbody></table></td></tr></tbody></table></td></tr></tbody></table></a><div class="yiv1401277158ydp7eec1b35card-controls-injection-wrapper" style="width:400px;z-index:3;min-height:0px;"><div class="yiv1401277158ydp7eec1b35p_a yiv1401277158ydp7eec1b35T_6Fd5 yiv1401277158ydp7eec1b35R_6Fd5"><div class="yiv1401277158ydp7eec1b35I_ak5mD yiv1401277158ydp7eec1b35e_dRA yiv1401277158ydp7eec1b35j_2kgqsw yiv1401277158ydp7eec1b35P_wpoVE" style="z-index:3;"><div class="yiv1401277158ydp7eec1b35P_Z1otACY yiv1401277158ydp7eec1b35H_6Fd5 yiv1401277158ydp7eec1b35W_6Fd5"><button tabindex="-1" class="yiv1401277158ydp7eec1b35c27KHO0_n yiv1401277158ydp7eec1b35b_0 yiv1401277158ydp7eec1b35M_0 yiv1401277158ydp7eec1b35i_0 yiv1401277158ydp7eec1b35I_T yiv1401277158ydp7eec1b35y_Z2uhb3X yiv1401277158ydp7eec1b35A_6EqO yiv1401277158ydp7eec1b35r_P yiv1401277158ydp7eec1b35C_q yiv1401277158ydp7eec1b35cvhIH6_T yiv1401277158ydp7eec1b35ir3_1JO2M7 yiv1401277158ydp7eec1b35P_0" title="Поділитися"><span class="yiv1401277158ydp7eec1b35D_F yiv1401277158ydp7eec1b35ab_C yiv1401277158ydp7eec1b35gl_C yiv1401277158ydp7eec1b35W_6D6F" style="width:16px;"></span></button></div></div></div></div></div><div style="font-family:Helvetica Neue, Helvetica, Arial, sans-serif;font-size:16px;"><br clear="none"></div><div dir="ltr" style="font-family:Helvetica Neue, Helvetica, Arial, sans-serif;font-size:16px;">so it works. And the library documentation says that a complexity of Cuckoo hash lookup is about <i>O(1)</i>, but with hashing there are questions of ratio of fulfilling the buckets and collisions.</div><div dir="ltr" style="font-family:Helvetica Neue, Helvetica, Arial, sans-serif;font-size:16px;"><br clear="none"></div><div dir="ltr" style="font-family:Helvetica Neue, Helvetica, Arial, sans-serif;font-size:16px;">So, my library having the very generic constraints can be used instead.</div><div dir="ltr" style="font-family:Helvetica Neue, Helvetica, Arial, sans-serif;font-size:16px;"><br clear="none"></div><div dir="ltr" style="font-family:Helvetica Neue, Helvetica, Arial, sans-serif;font-size:16px;">Best regards,</div><div dir="ltr" style="font-family:Helvetica Neue, Helvetica, Arial, sans-serif;font-size:16px;">Oleksandr Zhabenko.</div><div><br clear="none"></div></div></div><br clear="none"></div>
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субота, 21 вересня 2019 р., 21:52:18 GMT+3, olexandr543@yahoo.com <olexandr543@yahoo.com> написав:
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<div dir="ltr">Yes, you can. It needs another dependency and the complexity choice as <i>O(log (min (n, W)))</i> where W is a number of bits in a representing key, used for mapping. </div><div dir="ltr">For me, it is rather hard to solve whether it can be better, because it raises another problem of efficient binary representation of the keys.</div><div dir="ltr"><br clear="none"></div><div dir="ltr">While working on the topic, I found out that may be the most efficient will be hashing (for lookup it can be used e. g. Cuckoo hashing) and there is a library in Haskell for it.</div><div dir="ltr"><span><a rel="nofollow" shape="rect" class="yiv1401277158enhancr_card_9728930781" target="_blank" href="http://hackage.haskell.org/package/hashtables-1.2.3.4/docs/Data-HashTable-IO.html">Data.HashTable.IO</a> </span></div><div dir="ltr">Using it, you can write something like:</div><div dir="ltr"><br clear="none"></div><div dir="ltr"><div><div>{-# LANGUAGE ScopedTypeVariables #-}</div><div><br clear="none"></div><div>module Main where</div><div><br clear="none"></div><div>import qualified Data.HashTable.IO as I<br clear="none"></div><div>import Data.Maybe (fromJust,isJust)<br clear="none"></div><div>import System.Environment (getArgs)</div><div><br clear="none"></div><div>main :: IO ()<br clear="none"></div><div>main = do </div><div> args <- getArgs</div><div> let a = [([z,t],x) | x <- ['a'..'d'], z <- ['f'..'t'], t <- ['a'..'p'], [x,z,t] <= "fnf"] </div><div> b :: I.CuckooHashTable String Char <- I.fromList a </div><div> c <- I.lookup b ("kn") </div><div> let d1 u = do </div><div> d <- I.lookup b u</div><div> print c</div><div> if isJust d </div><div> then putStrLn . show . fromJust $ d </div><div> else putStrLn "Nothing"</div><div> return () </div><div> if null args </div><div> then d1 "fa"</div><div> else d1 (head $ args)</div></div><br clear="none"><div><br clear="none"></div><div class="yiv1401277158ydp5578d2f1yahoo-link-enhancr-card yiv1401277158ydp5578d2f1yahoo-link-enhancr-not-allow-cover yiv1401277158ydp5578d2f1ymail-preserve-class yiv1401277158ydp5578d2f1ymail-preserve-style" id="yiv1401277158ydp5578d2f1enhancr_card_9728930781" style="max-width:400px;font-family:Helvetica Neue, Segoe UI, Helvetica, Arial, sans-serif;" data-url="http://hackage.haskell.org/package/hashtables-1.2.3.4/docs/Data-HashTable-IO.html" data-type="YENHANCER" data-size="MEDIUM"><a rel="nofollow" shape="rect" class="yiv1401277158ydp5578d2f1yahoo-enhancr-cardlink" target="_blank" href="http://hackage.haskell.org/package/hashtables-1.2.3.4/docs/Data-HashTable-IO.html" style="text-decoration:none !important;color:#000 !important;"><table class="yiv1401277158ydp5578d2f1card-wrapper yiv1401277158ydp5578d2f1yahoo-ignore-table" border="0" cellpadding="0" cellspacing="0" style="max-width:400px;"><tbody><tr><td colspan="1" rowspan="1" width="400"><table class="yiv1401277158ydp5578d2f1card yiv1401277158ydp5578d2f1yahoo-ignore-table" border="0" cellpadding="0" cellspacing="0" width="100%" style="max-width:400px;border-width:1px;border-style:solid;border-color:rgb(224, 228, 233);border-radius:2px;"><tbody><tr><td colspan="1" rowspan="1"><table class="yiv1401277158ydp5578d2f1card-info yiv1401277158ydp5578d2f1yahoo-ignore-table" border="0" cellpadding="0" cellspacing="0" style="background:#fff;position:relative;z-index:2;width:100%;max-width:400px;border-radius:0 0 2px 2px;border-top:1px solid rgb(224, 228, 233);"><tbody><tr><td colspan="1" rowspan="1" style="background-color:#ffffff;padding:16px 0 16px 12px;vertical-align:top;border-radius:0 0 0 2px;"></td><td colspan="1" rowspan="1" style="vertical-align:middle;padding:12px 24px 16px 12px;width:99%;font-family:Helvetica Neue, Segoe UI, Helvetica, Arial, sans-serif;border-radius:0 0 2px 0;"><h2 class="yiv1401277158ydp5578d2f1card-title" style="font-size:14px;line-height:19px;margin:0px 0px 6px;font-family:Helvetica Neue, Segoe UI, Helvetica, Arial, sans-serif;color:rgb(38, 40, 42);">Data.HashTable.IO</h2><p class="yiv1401277158ydp5578d2f1card-description" style="font-size:12px;line-height:16px;margin:0px;color:rgb(151, 155, 167);"></p></td></tr></tbody></table></td></tr></tbody></table></td></tr></tbody></table></a></div><div><br clear="none"></div><div dir="ltr">so it works. And the library documentation says that a complexity of Cuckoo hash lookup is about <i>O(1)</i>, but with hashing there are questions of ratio of fulfilling the buckets and collisions.</div><div dir="ltr"><br clear="none"></div><div dir="ltr">So, my library having the very generic constraints can be used instead.</div><div dir="ltr"><br clear="none"></div><div dir="ltr">Best regards,</div><div dir="ltr">Oleksandr Zhabenko.</div><div dir="ltr"><br clear="none"></div><br clear="none"></div><div><br clear="none"></div>
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субота, 21 вересня 2019 р., 21:34:38 GMT+3, Henning Thielemann <lemming@henning-thielemann.de> написав:
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<div class="yiv1401277158yqt8700735078" id="yiv1401277158yqt58886"><div><div dir="ltr"><div class="yiv1401277158yqt0903812254" id="yiv1401277158yqtfd74755"><br clear="none">On Sat, 21 Sep 2019, olexandr543--- via Haskell wrote:<br clear="none"><br clear="none">> My library that can help to optimize using 'case ... of ...' construction if there are multiple (more than at<br clear="none">> least 5) variants.<br clear="none">> mm2: The library that can be used for optimization of multiple (Ord a) => a -> b transformations</div><br clear="none"><br clear="none">Isn't this a problem you would solve using Data.Map?<div class="yiv1401277158yqt0903812254" id="yiv1401277158yqtfd10236"><br clear="none"></div></div></div></div>
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