[GO pattern] Time Functions

package main

import (
    "log"
    "math/big"
    "time"
)

// Duration 测量程序运行时间
func Duration(invocation time.Time, name string) {
    elapsed := time.Since(invocation)
    log.Printf("%s lasted %s", name, elapsed)
}

func BigIntFactorial(x big.Int) *big.Int {
    defer Duration(time.Now(), "IntFactorial")

    y := big.NewInt(1)
    for one := big.NewInt(1); x.Sign() > 0; x.Sub(&x, one) {
        y.Mul(y, &x)
    }

    return x.Set(y)
}

func main() {
    BigIntFactorial(*big.NewInt(10000))
}