Home Articles FAQs XREF Games Software Instant Books BBS About FOLDOC RFCs Feedback Sitemap


You are here: irt.org | FOLDOC | sum

1. <theory> 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(x) -> E1; isB(x) -> E2}

This can be generalised to arbitrary numbers of domains.

See also smash sum, disjoint union.

2. <tool> 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).


Nearby terms: suit « suitably small « Suite Synthetique des Benchmarks de l'AFUU « sum » Summary Object Interchange Format » SUMMER » SUMMER SESSION

FOLDOC, Topics, A, B, C, D, E, F, G, H, I, J, K, L, M, N, O, P, Q, R, S, T, U, V, W, X, Y, Z, ?, ALL

©2018 Martin Webb