(Or "smash sum") In domain theory, the coalesced sum of domains A and B, A (+) B, contains all the non-bottom elements of both domains, tagged to show which part of the sum they come from, and a new bottom element. D (+) E = bottom U U 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)
