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)
