go集合处理举例

下面的代码以 string 为例，说明了 golang 在集合处理方面的函数和一些惯用法

package main

import "strings"
import "fmt"

// Index returns the first index of the target string `t`, or
// -1 if no match is found.
func Index(vs []string, t string) int {
    for i, v := range vs {
        if v == t {
            return i
        }
    }
    return -1
}

// Include returns `true` if the target string t is in the
// slice.
func Include(vs []string, t string) bool {
    return Index(vs, t) >= 0
}

// Any returns `true` if one of the strings in the slice
// satisfies the predicate `f`.
func Any(vs []string, f func(string) bool) bool {
    for _, v := range vs {
        if f(v) {
            return true
        }
    }
    return false
}

// All returns `true` if all of the strings in the slice
// satisfy the predicate `f`.
func All(vs []string, f func(string) bool) bool {
    for _, v := range vs {
        if !f(v) {
            return false
        }
    }
    return true
}

// Filter returns a new slice containing all strings in the
// slice that satisfy the predicate `f`.
func Filter(vs []string, f func(string) bool) []string {
    vsf := make([]string, 0)
    for _, v := range vs {
        if f(v) {
            vsf = append(vsf, v)
        }
    }
    return vsf
}

// Map returns a new slice containing the results of applying
// the function `f` to each string in the original slice.
func Map(vs []string, f func(string) string) []string {
    vsm := make([]string, len(vs))
    for i, v := range vs {
        vsm[i] = f(v)
    }
    return vsm
}

func main() {

    // Here we try out our various collection functions.
    var strs = []string{"peach", "apple", "pear", "plum"}

    fmt.Println(Index(strs, "pear"))

    fmt.Println(Include(strs, "grape"))

    fmt.Println(Any(strs, func(v string) bool {
        return strings.HasPrefix(v, "p")
    }))

    fmt.Println(All(strs, func(v string) bool {
        return strings.HasPrefix(v, "p")
    }))

    fmt.Println(Filter(strs, func(v string) bool {
        return strings.Contains(v, "e")
    }))

    // The above examples all used anonymous functions,
    // but you can also use named functions of the correct
    // type.
    fmt.Println(Map(strs, strings.ToUpper))

}

主要值得学习里面的 golang 函数式编程的惯用法，虽然 Python 中可以有更简洁的写法，
但是 golang 也支持，并且也没有繁琐很多，就已经很不错了。