_ = zb0001Mask
	if z.Prefix == "" {
		zb0001Len--
		zb0001Mask |= 0x2
	}
	// variable map header, size zb0001Len
	o = append(o, 0x80|uint8(zb0001Len))
	if zb0001Len == 0 {
		return
	}
	// string "bk"
	o = append(o, 0xa2, 0x62, 0x6b)
	o = msgp.AppendString(o, z.Bucket)
	if (zb0001Mask & 0x2) == 0 { // if not omitted
		// string "pr"
		o = append(o, 0xa2, 0x70, 0x72)

</pre>

<pre>
0.
72.40
072.40       // == 72.40
2.71828
1.e+0
6.67428e-11
1E6
.25
.12345E+5
1_5.         // == 15.0
0.15e+0_2    // == 15.0

0x1p-2       // == 0.25
0x2.p10      // == 2048.0
0x1.Fp+0     // == 1.9375
0X.8p-0      // == 0.5
0X_1FFFP-16  // == 0.1249847412109375
0x15e-2      // == 0x15e - 2 (integer subtraction)

0x.p1        // invalid: mantissa has no digits