[mkgmap-dev] value (string) handling via style file

Moin, I want to do some modifications of the tag-values via the style file. I know this has been a topic here before, but I can not find the neccessary hints right know. - How can I check the first character of the value in a style file? (I want to detect whether the first character is a minus sign "-".) - How can I check the last character of the value in a style file? (incline allows either "%" or "°") - How can I remove the first character of the value in a style file? ("-5%" -> "5%") - How can I check, whether a character is numeric? (in [0..9]) Can anybody help me? Gruss Torsten PS: The definition of the incline tag is really a nightmare for automated evaluation.