http://dev.clojure.org/jira This file is an XML representation of an issue en-us 4.4 649 25-07-2011 http://dev.clojure.org/jira/browse/LOGIC-113 core.logic <div class="code panel" style="border-width: 1px;"><div class="codeContent panelContent"> <pre class="code-java">(ns test (:refer-clojure :exclude [==]) (:require [clojure.core.logic :refer :all])) ;; This expression should evaluate to <span class="code-keyword">true</span>, but it does not, ;; because the second run* returns (2 1) instead of (1 2). (= (run* [q] (conde [(== q 1)] [(== q 2)])) (run* [q] (conde [(fresh [a] (== q 1))] [(== q 2)])))</pre> </div></div> tested against HEAD (0.8.0-rc3-SNAPSHOT) and CLJ 1.5.0-RC15 LOGIC-113

A conde clause that beings with a fresh expression will initially fail

Defect Major Resolved Declined David Nolen Austin Haas Wed, 13 Feb 2013 23:49:43 -0600 Fri, 15 Feb 2013 12:49:03 -0600 Fri, 15 Feb 2013 12:49:03 -0600 0 1 <p>This is not an error. No promises are made about the order of results. If you want need to verify that two runs are the same it's best to put the results into a set - we actually do this in the tests now.</p> <p>Shouldn't the programmer be able to reason about the order that the clauses will be tried? That's one way to direct the search and I know at least one example in TRS highlights that aspect--in Ch. 5, unwrapo is re-written to push the recursive call down, otherwise it diverges. How could you know that goal will terminate if you can't reason about the order of the clauses? I assume it is much more difficult to write exclusively non-overlapping clauses.</p> <p>Likewise, shouldn't the programmer be able to design a logic program so that it produces a predictable first result?</p> <p>This is all very new to me, so please forgive me if I'm way off.</p> <p>miniKanren makes no promises about order anymore, Will actually talks about this in his dissertation. It's part of the design and leaves the door wide open for concurrent search when we get there.</p> <p>Even so, I do understand there are cases where the programmer might want more control than is provided by the default behavior. Customizable search is on the roadmap.</p> <p>But the current default behavior is expected and unlikely to change.</p> <p>Not a bug.</p> Global Rank