Breakdown of float64 (IEEE 754 double-precision binary floating-point format)

float64debug.go

package main

import (
	"fmt"
	"math"
)

const float64MantissaMask =    0xFFFFFFFFFFFFF
const float64ExponentMask = 0x7FF0000000000000
const float64SignMask     = 0x8000000000000000
const float64ExponentBitOffset = 52
const float64ExponentValueOffset = -1023
const float64SignOffset = 63

func main() {
	floatDebug(math.Pi)
}

func floatDebug(bar float64) {
	barBits := math.Float64bits(bar)
	fmt.Printf("Value    : %f\n", bar)
	fmt.Printf("Bits     : %X\n", barBits)
	fmt.Printf("Mantissa : %X\n", barBits&float64MantissaMask)
	fmt.Printf("Exponent : %X\n", (int64(barBits&float64ExponentMask)>>float64ExponentBitOffset)+float64ExponentValueOffset)
	fmt.Printf("Sign     : %X\n", (barBits&float64SignMask)>>float64SignOffset)
}

Value    : 3.141593
Bits     : 400921FB54442D18
Mantissa : 921FB54442D18
Exponent : 1
Sign     : 0