# numbers in Kanji

I'm trying to develop an API to normalize Japanese numbers into arabic numbers. Since I'm not familiar with Japanese numbers, there are three questions for which I did not find an answer:

1. How do we write negative numbers in kanji ? for example, what would be the syntax of -1234 ? Does one use the minus sign as in English, or some other sign like 負 ?
2. For the decimal separator, I read many things, and the source do not have the same answer: some say that it can be as in English, so for example "三千2百２十.三" will be equal to "3220.3". Some other source say that the separator is "點" or "点" and hence "七十五點四〇二五" is equal to "75.4025". So should I support the three characters as decimal separator ?
3. About the zero, which one is really used ? "零" or "〇" ?

Kanji is no longer actively used to represent complicated numbers in most part of our daily life, and it's not a suitable way to describe numbers in technical contexts. Kanji numbers are still used in vertical writing. When people really need to write negative fractional numbers in modern vertically-written materials (e.g. novels and newspapers), `-43.05`, for example, will usually look like this:
Katakana マイナス indicates the number is negative, and a centered dot ("中黒") is used in place of the decimal sign. (By the way, 点 "ten" is the reading of this sign, not the actual symbol you write.) The pseudo-kanji `〇` is usually used in this context. This is a relatively recent convention only used in vertical writing. The same thing written horizontally (`マイナス四三・〇五`) looks pretty unnatural.