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HomeBackend DevelopmentGolangGolang regexp MatchString() is not idempotent

Golang regexp MatchString() 不是幂等的

问题内容

我不知道发生了什么。使用golang的regexp库时,相同的函数相同的输入返回不同的结果。

package main

import (
    "fmt"
    "regexp"
)

type paymentnetworkdata struct {
    regex string
    name  string
}

var payment_networks = map[string]paymentnetworkdata{
    "mastercard": {
        regex: "^5[1-5][0-9]{14}|^(222[1-9]|22[3-9]\\d|2[3-6]\\d{2}|27[0-1]\\d|2720)[0-9]{12}$",
        name:  "mastercard",
    },
    "visamaster": {
        regex: "^(?:4[0-9]{12}(?:[0-9]{3})?|5[1-5][0-9]{14})$",
        name:  "visamaster",
    },
}

func resolvepaymentnetwork(cardin string) string {
    paynet := "unknown"
    for _, v := range payment_networks {
        regex := regexp.mustcompile(v.regex)

        if regex.matchstring(cardin) {
            paynet = v.name
        }
    }
    return paynet
}

func main() {

    in := "5103901404433835"

    for i := 1; i < 100; i++ {
        paynet := resolvepaymentnetwork(in)
        fmt.println("payment network is: ", paynet)
    }
}

输入:5103901404433835

正则表达式:

mastercard: ^5[1-5][0-9]{14}|^(222[1-9]|22[3-9]\\d|2[3-6]\\d{2}|27[0-1]\\d|2720)[0-9]{12}$
visamaster: ^(?:4[0-9]{12}(?:[0-9]{3})?|5[1-5][0-9]{14})$

go 语言输出:

payment network is:  visamaster
payment network is:  mastercard
payment network is:  mastercard
payment network is:  visamaster
payment network is:  visamaster
payment network is:  visamaster
payment network is:  visamaster
payment network is:  visamaster
payment network is:  visamaster

我使用 nodejs 测试了相同的代码,在本例中结果始终相同。

js 输出:

Payment Network is:  VisaMaster
Payment Network is:  VisaMaster
Payment Network is:  VisaMaster
Payment Network is:  VisaMaster
Payment Network is:  VisaMaster
Payment Network is:  VisaMaster
Payment Network is:  VisaMaster
Payment Network is:  VisaMaster
Payment Network is:  VisaMaster
Payment Network is:  VisaMaster
  • go 代码演示:https://go.dev/play/p/up4g0jowlv_l
  • js 代码演示:https://playcode.io/1450178

正确答案


您的代码有几个问题:

  1. 没有明显原因使用 map
  2. 两个正则表达式都与提供的卡号匹配。

这些问题,以及通过映射迭代不能保证产生相同序列的事实,导致函数非幂等。

这是更正后的代码:

package main

import (
    "fmt"
    "regexp"
)

type PaymentNetworkData struct {
    Regex *regexp.Regexp
    Name  string
}

var PAYMENT_NETWORKS = [2]PaymentNetworkData{
    {
        Regex: regexp.MustCompile("^(?:5[1-5][0-9]{14}|(?:222[1-9]|22[3-9]\\d|2[3-6]\\d{2}|27[0-1]\\d|2720)[0-9]{12})$"),
        Name:  "Mastercard",
    },
    {
        Regex: regexp.MustCompile("^(?:4[0-9]{12}(?:[0-9]{3})?|5[1-5][0-9]{14})$"),
        Name:  "VisaMaster",
    },
}

func resolvePaymentNetwork(cardIn string) string {
    for _, v := range PAYMENT_NETWORKS {
        if v.Regex.MatchString(cardIn) {
            return v.Name
        }
    }
    return "Unknown"
}

func main() {
    in := "5103901404433835"

    for i := 1; i < 100; i++ {
        payNet := resolvePaymentNetwork(in)
        fmt.Println("Payment Network is: ", payNet)
    }
}

它使用数组而不是映射来保证顺序。

此外,我还更改了您的结构,使其仅编译一次正则表达式。

每次输出payment network为:mastercard

演示此处

注意,它仍然使用相同的正则表达式(由 评论中的@wiktorstribiżew)。它们看起来不太好,尤其是这部分 (?:4[0-9]{12}(?:[0-9]{3})? - 它也会匹配 13 位数字。
您最好检查卡号的预期格式,并相应地更正表达式。

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