英文:
How to increment using 'functional programming' in golang
问题
我从exercism得到了一个代码挑战，题目是“利息很有趣”。我尽量使用函数式编程的方法来解决问题，但是我发现我的最后一个函数使用了两个可变变量。
package interest
import "math"
// InterestRate返回提供的余额的利率。
func InterestRate(balance float64) float32 {
switch {
case balance < 0:
return 3.213
case balance < 1000:
return 0.5
case balance < 5000:
return 1.621
default:
return 2.475
}
}
// Interest计算提供的余额的利息。
func Interest(balance float64) float64 {
if balance < 0 {
return -math.Abs(balance) * float64(InterestRate(balance)) / 100.0
}
return math.Abs(balance) * float64(InterestRate(balance)) / 100.0
}
// AnnualBalanceUpdate计算年度余额更新，考虑到利率。
func AnnualBalanceUpdate(balance float64) float64 {
return balance + Interest(balance)
}
// YearsBeforeDesiredBalance计算达到目标余额所需的最少年数：
func YearsBeforeDesiredBalance(balance, targetBalance float64) int {
year := 0
for balance < targetBalance {
balance = AnnualBalanceUpdate(balance)
year++
}
return year
}
我的代码还有更多的函数式编程方法吗？
英文:
I got a code challenge from exercism title: Interest is interesting. I solved the questions with extra challenge from myself: use functional approach as much as possible. However, I found my last function use two mutable variables.
package interest
import "math"
// InterestRate returns the interest rate for the provided balance.
func InterestRate(balance float64) float32 {
switch {
case balance < 0:
return 3.213
case balance < 1000:
return 0.5
case balance < 5000:
return 1.621
default:
return 2.475
}
}
// Interest calculates the interest for the provided balance.
func Interest(balance float64) float64 {
if balance < 0 {
return -math.Abs(balance) * float64(InterestRate(balance)) / 100.0
}
return math.Abs(balance) * float64(InterestRate(balance)) / 100.0
}
// AnnualBalanceUpdate calculates the annual balance update, taking into account the interest rate.
func AnnualBalanceUpdate(balance float64) float64 {
return balance + Interest(balance)
}
// YearsBeforeDesiredBalance calculates the minimum number of years required to reach the desired balance:
func YearsBeforeDesiredBalance(balance, targetBalance float64) int {
year := 0
for balance < targetBalance {
balance = AnnualBalanceUpdate(balance)
year++
}
return year
}
Is there any more 'functional programming' approach for my codes?
答案1
得分: 2
递归通常用于这个目的：
func YearsBeforeDesiredBalance(balance, targetBalance float64, year int) int {
if balance >= targetBalance {
return year
}
return YearsBeforeDesiredBalance(AnnualBalanceUpdate(balance), targetBalance, year + 1)
}
请注意，Go语言不是一种函数式编程语言，可能不会对这种递归进行优化。
英文:
Recursion is usually used for this:
func YearsBeforeDesiredBalance(balance, targetBalance float64, year int) int {
if balance >= targetBalance {
return year
}
return YearsBeforeDesiredBalance(AnnualBalanceUpdate(balance), targetedBalance, year + 1)
}
Mind that Go is not a functional programming language and probably does not optimize this kind of recursion.
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