Word-wrapping (or line-folding) is one of frequently used text-processing. It is implemented very easily only when it is based on several assumptions such as:

    * One character consists from one byte.
    * One character occupies one column on the terminal.
    * A line can be folded between words which are separated by whitespaces.

All of these assumptions are local and valid only for some part of languages in the world. There are languages which don't meet the assumptions and speakers of such languages cannot use softwares which depend on these assumptions.

Since it is usually difficult to require developers to know various languages in the world and their properties, text-processing algorithms should be supplied as libraries. Otherwise, their softwares cannot support various languages in the world and people in the world suffer from a problem that many softwares are useless for them.