localising currency (help me out)

It seems there are no utilities around to localise currency (correct me if I’m wrong, I’m writing in C), so I’m having to write my own. Regardless of the system localisation, I want to be able to refer to a currency (for which I have the currency code) in a localised way.

Thus, what I’m looking for is for your 3-letter currency code, how do you refer to positive and negative numbers? For example, in AUD it would be “$1.25” and “−$1.25”.