numeration system
A numeration system is a triple , where is a positive integer, is a non-empty alphabet, and is a one-to-one function from to the set of non-negative integers . Order elements of so that their values are in increasing order:
, where for .
is called the base of numeration system , and the elements the digits of . Words over are called numeral words.
Given a numeral word with , the integer non-negative is said to be represented by if
An integer is said to be representable in if there is a numeral word representing .
Examples.
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Just as common is the binary digital system: where again is the identity function.
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In fact, any digital system is a numeration system , where and .
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Consider the system , where . Since any word over is just a string of ’s, consecutive strings of represent . We conclude that the integers representable by have the form for any positive integer .
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Consider the system
where . It is easy to see that every integer is representable by . However, some integers may be represented by more than one numeral words. For example,
The numeration system is used by the Chinese.
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Consider the system where . Then . Notice that can not be represented . Also, note that .
A numeration system is said to be complete if every non-negative integer has at least one representation in ; and unambiguous if every non-negative integer has at most one representation in . is ambiguous if is not unambiguous. Every digital system is complete and unambiguous. In the examples above, is complete but ambiguous; is unambiguous but not complete; is neither complete nor unambiguous.
Remark. Representation non-negative integers by a numeration system can be extended to rational numbers. The corresponding concepts of completeness and ambiguity may be defined similarly.
References
- 1 A. Salomaa Computation and Automata, Encyclopedia of Mathematics and Its Applications, Vol. 25. Cambridge (1985).
Title | numeration system |
Canonical name | NumerationSystem |
Date of creation | 2013-03-22 18:57:46 |
Last modified on | 2013-03-22 18:57:46 |
Owner | CWoo (3771) |
Last modified by | CWoo (3771) |
Numerical id | 8 |
Author | CWoo (3771) |
Entry type | Definition |
Classification | msc 11A67 |
Synonym | numeral system |
Synonym | number system |
Related topic | Base3 |
Defines | base |
Defines | digit |
Defines | complete numeration system |
Defines | unambiguous numeration system |
Defines | ambiguous numeration system |