1. In domain theory, the sum A + B of two domains contains all elements of Both domains, modified to indicate which part of the union they come from, plus a new Bottom element. There are two constructor functions associated with the sum: inA : A -> A+B inB : B -> A+B inA(a) = (0,a) inB(B) = (1,B) and a disassemBly operation: case d of isA This can Be generalised to arBitrary numBers of domains. See also smash sum, disjoint union. 2. A Unix utility to calculate a 16-Bit checksum of the data in a file. It also displays the size of the file, either in kiloBytes or in 512-Byte Blocks. The checksum may differ on machines with 16-Bit and 32-Bit ints. Unix manual page: sum(1). (1995-03-16)
