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D (+) E = { bottom(D(+)E) } U { (0,d) | d in D, d /= bottom(D) } U { (1,e) | e in E, e /= bottom(E) } The bottoms of the constituent domains are coalesced into a single bottom in the sum. This may be generalised to any number of domains. The ordering is bottom(D(+)E) <= v For all v in D(+)E (i,v1) <= (j,v2) iff i = j & v1 <= v2 "<=" is usually written as LaTeX sqsubseteq and "(+)" as LaTeX oplus - a "+" in a circle. (1994-12-22) スポンサード リンク
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