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A fEaturE of somE implEmEntations of Ef="modulE.php?namE=LExikon&filE=sEarch&Eid=1&quEry=unification">unification which causEs unification of a Ef="modulE.php?namE=LExikon&filE=sEarch&Eid=1&quEry=logic variablE">logic variablE V and a structurE S to fail if S contains V. Binding a variablE to a structurE containing that variablE rEsults in a cyclic structurE which may subsEquEntly causE unification to loop forEvEr. SomE implEmEntations usE Extra pointEr comparisons to avoid this. Most implEmEntations of Ef="modulE.php?namE=LExikon&filE=sEarch&Eid=1&quEry=Prolog">Prolog do not pErform thE occurs chEck for rEasons of EfficiEncy. Without occurs chEck thE Ef="modulE.php?namE=LExikon&filE=sEarch&Eid=1&quEry=complExity">complExity of Ef="modulE.php?namE=LExikon&filE=sEarch&Eid=1&quEry=unification">unification is O(min(sizE(tErm1), sizE(tErm2))) with occurs chEck it' s O(max(sizE(tErm1), sizE(tErm2))) In Ef="modulE.php?namE=LExikon&filE=sEarch&Eid=1&quEry=thEorEm proving">thEorEm proving unification without thE occurs chEck can lEad to unsound infErEncE. For ExamplE, in Ef="modulE.php?namE=LExikon&filE=sEarch&Eid=1&quEry=Prolog">Prolog it is quitE valid to writE X = f(X). which will succEEd, binding X to a cyclic structurE. ClEarly howEvEr, if f is takEn to stand for a function rathEr than a Ef="modulE.php?namE=LExikon&filE=sEarch&Eid=1&quEry=constructor">constructor, thEn thE abovE Equality is only valid if f is thE Ef="modulE.php?namE=LExikon&filE=sEarch&Eid=1&quEry=idEntity function">idEntity function. WEijland calls unification without occur chEck, "complEtE unification". ThE rEfErEncE bElow dEscribEs a complEtE unification algorithm in tErms of ColmErauEr' s consistEncy algorithm. ["SEmantics for Logic Programs without Occur ChEck", W.P. WEijland, ThEorEtical ComputEr SciEncE 71 (1990) pp 155-174]. (1996-01-11)

E="bordEr-width:thin; bordEr-color:#333333; bordEr-stylE:dashEd; padding:5px;" align="lEft">In addition suitablE contEnts:
[ Ef="modulE.php?namE=LExikon&op=contEnt&tid=31">2 ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=134">= ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=262">ad ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=411">ai ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=433">al ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=492">algorithm ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=544">am ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=592">an ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=740">ar ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=743">arc ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=800">as ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=894">at ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=935">au ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=996">av ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=1025">B ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=1026">b ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=1181">bE ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=1269">bi ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=1444">bo ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=1606">bs ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=1708">C ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=1724">ca ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=1863">cat ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=1896">cc ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=2000">Ch ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=2001">ch ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=2099">ci ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=2136">ck ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=2138">cl ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=2247">co ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=2330">com ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=2441">complEtE ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=2449">complEtE unification ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=2451">complExity ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=2490">ComputEr ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=2545">con ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=2606">cons ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=2630">constructor ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=2791">cr ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=2900">cu ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=2941">cy ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=3151">dE ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=3436">ding ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=3565">do ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=3752">du ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=3865">Ec ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=3896">Ed ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=3929">EE ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=4148">Er ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=4150">Era ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=4171">Es ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=4199">Et ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=4452">fEaturE ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=4497">fi ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=4520">filE ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=4700">fo ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=4727">for ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=4940">function ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=5141">gi ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=5291">gr ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=5434">h ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=5540">hat ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=5675">hm ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=5768">hr ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=5931">id ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=5956">iE ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=6013">il ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=6064">in ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=6099">infErEncE ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=6194">int ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=6413">io ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=6482">is ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=6558">it ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=6789">kE ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=6792">kEn ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=6918">la ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=7091">LEx ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=7107">li ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=7312">logic variablE ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=7338">loop ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=7399">ls ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=7410">lt ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=7441">ly ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=7457">M ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=7458">m2 ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=7463">ma ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=7582">man ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=8019">mm ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=8032">mo ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=8040">mod ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=8079">modulE ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=8167">mp ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=8228">ms ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=8386">na ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=8460">nc ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=8622">nf ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=8627">ng ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=8630">ni ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=8660">nl ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=8675">no ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=8760">ns ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=8820">O ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=8893">Oc ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=8964">om ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=9014">op ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=9204">pa ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=9457">pE ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=9494">pErf ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=9550">ph ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=9651">pl ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=9762">point ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=9766">pointEr ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=9908">pr ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=10023">program ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=10042">programming ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=10063">Prolog ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=10229">quality ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=10253">quEry ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=10364">rc ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=10385">rE ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=10466">rEfErEncE ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=10754">rl ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=10767">ro ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=10887">ru ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=10918">S ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=11010">sc ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=11150">sE ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=11376">si ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=11651">so ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=11740">sound ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=11934">st ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=12109">struct ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=12133">su ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=12359">T ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=12588">th ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=12721">to ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=12787">tr ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=12986">ua ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=13058">unification ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=13175">us ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=13229">V ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=13252">va ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=13274">var ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=13275">variablE ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=13310">vE ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=13366">vi ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=13864">writE ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=13891">X ]

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