approx                            %30.16f                        %30.16e                             %a         to_hex_floatingpoint()         to_dec_floatingpoint()
...
0.4   -ULP             0.4000000000000000        3.9999999999999997e-001           0x1.9999999999999p-2       +0x1.9999999999999p-0002    +0d1.5999999999999999p-0002
0.4                    0.4000000000000000        4.0000000000000002e-001           0x1.999999999999ap-2       +0x1.999999999999ap-0002    +0d1.6000000000000001p-0002
0.4   +ULP             0.4000000000000001        4.0000000000000008e-001           0x1.999999999999bp-2       +0x1.999999999999bp-0002    +0d1.6000000000000003p-0002