Write some Software

I need a program to manipulate library classification numbers, such as the Dewey-decimal classification system. Under such a classification system, an area of knowledge is subdivided into a hierarchy of sub-areas, sub-sub-areas and so on. Each little field is given a code, such that the code of a parent field is a prefix of the codes of the sub-fields within that field. For example, here is a (hypothetical) hierarchy of classifications and codes: Code Classification 0 Science 01 Physics 02 Computing 020 Computer hardware 021 Computer languages 0210 Imperative languages 0211 Functional languages 02110 Haskell 02111 ML 02112 Scala 022 Artificial Intelligence 03 Mathematics 1 Arts 2 Religion