3.3 四舍五入

package main

import (
    "fmt"
    "math"
)

var valA float64 = 3.55554444

func main() {

    // Bad assumption on rounding
    // the number by casting it to
    // integer.
    intVal := int(valA)
    fmt.Printf("Bad rounding by casting to int: %v\n", intVal)

    fRound := Round(valA)
    fmt.Printf("Rounding by custom function: %v\n", fRound)

}

// Round returns the nearest integer.
func Round(x float64) float64 {
    t := math.Trunc(x)
    if math.Abs(x-t) >= 0.5 {
        return t + math.Copysign(1, x)
    }
    return t
}

/*
Bad rounding by casting to int: 3
Rounding by custom function: 4

*/