You cannot select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
114 lines
2.7 KiB
Go
114 lines
2.7 KiB
Go
// We often need our programs to perform operations on
|
|
// collections of data, like selecting all items that
|
|
// satisfy a given predicate or mapping all items to a new
|
|
// collection with a custom function.
|
|
|
|
// In some languages it's idiomatic to use [generic](http://en.wikipedia.org/wiki/Generic_programming)
|
|
// data structures and algorithms. Go does not support
|
|
// generics; in Go it's common to provide collection
|
|
// functions if and when they are specifically needed for
|
|
// your program and data types.
|
|
|
|
// Here are some example collection functions for slices
|
|
// of `strings`. You can use these examples to build your
|
|
// own functions. Note that in some cases it may be
|
|
// clearest to just inline the collection-manipulating
|
|
// code directly, instead of creating and calling a
|
|
// helper function.
|
|
|
|
package main
|
|
|
|
import (
|
|
"fmt"
|
|
"strings"
|
|
)
|
|
|
|
// 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))
|
|
|
|
}
|