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The Wiki page (https://github.com/clojure/core.logic/wiki/A-Core.logic-Primer#corelogic-is-declarative) says "...the order of constraints does not matter as far as the value of the (run* ...) expression is concerned." But I tried this example of Sudoku solver (https://gist.github.com/orb/5884956) and found that if you exchange these two lines:
(everyg #(fd/in % sdnum) board) (init-board board puzzle)
{{core.logic}} will freeze and never return the answer.