If *** is a binary code of length
, a "soft decision" decoding algorithm for *** changes an arbitrary point of
into a nearest codeword (nearest in Euclidean distance).
Similarly, a decoding algorithm for a lattice
in
changes an arbitrary point of
into a closest lattice point. Some general methods are given for constructing such algorithms, ami are used to obtain new and faster decoding algorithms for the Gosset lattice
, the Golay code the Leech lattice.