String encoding of primitive types preserving lexicographic order

Question

Does anyone know of a library for encoding a number of primitive types (like integers, floats, strings, etc) into a string but preserving the lexicographical order of the types?

Ideally, I'm looking for a C++ library, but other languages are fine too. Also, one can assume that the format does not need to be encoded in the string itself (that is, if it's int64/string/float then the encoded string does not need to encode this information, only encoding the data is enough).

Answer 1

Just write numeric values in a fixed column width with leading zeros, and strings as normal. So like this:

0.1 -> 0000000.1000000
123 -> 0000123.0000000
foo -> foo
X   -> X

Then you can sort as text (e.g. Unix sort without -n). How about that?

Answer 2

Take a look at this paper ("Efficient Lexicographic Encoding of Numbers") which shows how to represent any numeric type as a string such the lexicographic order of the strings is the same as the numerical order of the underlying numbers. It copes with arbitrary length numbers.

http://www.zanopha.com/docs/elen.pdf