Codes and Their Extensions
The extension of a code is the mapping of finite length source sequences to finite length bit strings, that is obtained by concatenating for each symbol of the source sequence the corresponding codeword produced by the original code.
Using terms from formal language theory, the precise mathematical definition is as follows: Let and be two finite sets, called the source and target alphabets, respectively. A code is a total function mapping each symbol from to a sequence of symbols over, and the extension of to a homomorphism of into, which naturally maps each sequence of source symbols to a sequence of target symbols, is referred to as its extension.
Read more about this topic: Variable-length Code
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