locale: decimal comma vs. point

If I export a label track from Audacity the time stamps are formatted with decimal commas instead of decimal points. E.g. 1.5s is formatted as "1,5" not "1.5". I guess this is because I have German locale as default. I want to write numbers from Haskell compatible to this format and thus I want to know whether I have to format numbers with decimal commas or decimal points. However an according information or even better, a locale-aware printf seems to be missing in old-locale. :-(