 Set (or clear) an amount's display decimal point.
setAmountDecimalPoint :: Maybe Char -> Amount -> Amount
setAmountDecimalPoint mc a@Amount{ astyle=s } = a{ astyle=s{asdecimalpoint=mc} }

--
setAmountDecimalPoint :: Maybe Char -> Amount -> Amount
setAmountDecimalPoint mc a@Amount{ astyle=s } = a{ astyle=s{asdecimalpoint=mc} }
setAmountDecimalPoint mc a@Amount{ astyle=s } = a{ astyle=s{asdecimalpoint=mc} }