showEFloat +base

showEFloat :: RealFloat a => Maybe Int -> a -> ShowS
base Numeric
Show a signed RealFloat value using scientific (exponential) notation (e.g. 2.45e2, 1.5e-3). In the call showEFloat digs val, if digs is Nothing, the value is shown to full precision; if digs is Just d, then at most d digits after the decimal point are shown.