Rust vs Go:常用语法对比(二)
21. Swap values
交换变量a和b的值
a, b = b, a
package main
import "fmt"
func main() {
a := 3
b := 10
a, b = b, a
fmt.Println(a)
fmt.Println(b)
}
10
3
fn main() {
let a = 3;
let b = 10;
let (a, b) = (b, a);
println!("a: {a}, b: {b}", a=a, b=b);
}
输出
a: 10, b: 3
or
fn main() {
let (a, b) = (12, 42);
println!("a = {}, b = {}", a, b);
let (a, b) = (b, a);
println!("a = {}, b = {}", a, b);
}
输出
a = 12, b = 42
a = 42, b = 12
22. Convert string to integer
将字符串转换为整型
import "strconv"
i, err := strconv.Atoi(s)
package main
import (
"fmt"
"reflect"
"strconv"
)
func main() {
// create a string
s := "123"
fmt.Println(s)
fmt.Println("type:", reflect.TypeOf(s))
// convert string to int
i, err := strconv.Atoi(s)
if err != nil {
panic(err)
}
fmt.Println(i)
fmt.Println("type:", reflect.TypeOf(i))
}
123
type: string
123
type: int
or
import "strconv"
i, err := strconv.ParseInt(s, 10, 0)
package main
import (
"fmt"
"reflect"
"strconv"
)
func main() {
s := "123"
fmt.Println("s is", reflect.TypeOf(s), s)
i, err := strconv.ParseInt(s, 10, 0)
if err != nil {
panic(err)
}
fmt.Println("i is", reflect.TypeOf(i), i)
}
s is string 123
i is int64 123
fn main() {
// This prints 123
let mut s = "123";
let mut i = s.parse::<i32>().unwrap();
println!("{:?}", i);
// This panics
s = "12u3";
i = s.parse::<i32>().unwrap();
println!("{:?}", i);
}
输出
123
thread 'main' panicked at 'called `Result::unwrap()` on an `Err` value: ParseIntError { kind: InvalidDigit }', src/libcore/result.rs:860
note: Run with `RUST_BACKTRACE=1` for a backtrace.
or
fn main() {
let mut s = "123";
let mut i: i32 = s.parse().unwrap_or(0);
println!("{:?}", i);
s = "12u3";
i = s.parse().unwrap_or(0);
println!("{:?}", i);
}
输出
123
0
or
fn main() {
let mut s = "123";
let mut i = match s.parse::<i32>() {
Ok(i) => i,
Err(_e) => -1,
};
println!("{:?}", i);
s = "12u3";
i = match s.parse::<i32>() {
Ok(i) => i,
Err(_e) => -1,
};
println!("{:?}", i);
}
输出
123
-1
23. Convert real number to string with 2 decimal places
Given a real number x, create its string representation s with 2 decimal digits following the dot.
给定一个实数，小数点后保留两位小数
package main
import "fmt"
func main() {
x := 3.14159
s := fmt.Sprintf("%.2f", x)
fmt.Println(s)
}
输出
3.14
fn main() {
let x = 42.1337;
let s = format!("{:.2}", x);
println!("{}", s);
}
输出
42.13
24. Assign to string the japanese word ネコ
Declare a new string s and initialize it with the literal value "ネコ" (which means "cat" in japanese)
声明一个新的字符串s，并用文字值“ネコ”初始化它(在日语中是“cat”的意思)
package main
import "fmt"
func main() {
s := "ネコ"
fmt.Println(s)
}
fn main() {
let s = "ネコ";
println!("{}", s);
}
25. Send a value to another thread
Share the string value "Alan" with an existing running process which will then display "Hello, Alan"
将字符串值“Alan”与现有的正在运行的进程共享，该进程将显示“你好，Alan”
ch <- "Alan"
package main
import (
"fmt"
"time"
)
func main() {
ch := make(chan string)
go func() {
v := <-ch
fmt.Printf("Hello, %v\n", v)
}()
ch <- "Alan"
// Make sure the non-main goroutine had the chance to finish.
time.Sleep(time.Second)
}
Hello, Alan
The receiver goroutine blocks reading the string channel ch. The current goroutine sends the value to ch. A goroutine is like a thread, but more lightweight.
use std::thread;
use std::sync::mpsc::channel;
fn main() {
let (send, recv) = channel();
let handle = thread::spawn(move || loop {
let msg = recv.recv().unwrap();
println!("Hello, {:?}", msg);
});
send.send("Alan").unwrap();
handle.join().unwrap();
}
输出 Hello, "Alan"
26. Create a 2-dimensional array
Declare and initialize a matrix x having m rows and n columns, containing real numbers.
创建一个二维数组
声明并初始化一个有m行n列的矩阵x，包含实数。
const m, n = 3, 4
var x [m][n]float64
package main
import "fmt"
func main() {
const m, n = 3, 4
var x [m][n]float64
x[1][2] = 8
fmt.Println(x)
}
[[0 0 0 0] [0 0 8 0] [0 0 0 0]]
or
package main
import "fmt"
func main() {
x := make2D(2, 3)
x[1][1] = 8
fmt.Println(x)
}
func make2D(m, n int) [][]float64 {
buf := make([]float64, m*n)
x := make([][]float64, m)
for i := range x {
x[i] = buf[:n:n]
buf = buf[n:]
}
return x
}
[[0 0 0] [0 8 0]]
fn main() {
const M: usize = 4;
const N: usize = 6;
let x = vec![vec![0.0f64; N]; M];
println!("{:#?}", x);
}
输出
[
[
0.0,
0.0,
0.0,
0.0,
0.0,
0.0,
],
[
0.0,
0.0,
0.0,
0.0,
0.0,
0.0,
],
[
0.0,
0.0,
0.0,
0.0,
0.0,
0.0,
],
[
0.0,
0.0,
0.0,
0.0,
0.0,
0.0,
],
]
fn main() {
const M: usize = 3;
const N: usize = 4;
let mut x = [[0.0; N] ; M];
x[1][3] = 5.0;
println!("{:#?}", x);
}
输出
[
[
0.0,
0.0,
0.0,
0.0,
],
[
0.0,
0.0,
0.0,
5.0,
],
[
0.0,
0.0,
0.0,
0.0,
],
]
27. Create a 3-dimensional array
Declare and initialize a 3D array x, having dimensions boundaries m, n, p, and containing real numbers.
创建一个三维数组
声明并初始化一个三维数组x，它有m，n，p维边界，并且包含实数。
const m, n, p = 2, 2, 3
var x [m][n][p]float64
package main
import "fmt"
func main() {
const m, n, p = 2, 2, 3
var x [m][n][p]float64
x[1][0][2] = 9
// Value of x
fmt.Println(x)
// Type of x
fmt.Printf("%T", x)
}
[[[0 0 0] [0 0 0]] [[0 0 9] [0 0 0]]]
[2][2][3]float64
or
func make3D(m, n, p int) [][][]float64 {
buf := make([]float64, m*n*p)
x := make([][][]float64, m)
for i := range x {
x[i] = make([][]float64, n)
for j := range x[i] {
x[i][j] = buf[:p:p]
buf = buf[p:]
}
}
return x
}
package main
import "fmt"
func main() {
x := make3D(2, 2, 3)
x[1][0][2] = 9
fmt.Println(x)
}
func make3D(m, n, p int) [][][]float64 {
buf := make([]float64, m*n*p)
x := make([][][]float64, m)
for i := range x {
x[i] = make([][]float64, n)
for j := range x[i] {
x[i][j] = buf[:p:p]
buf = buf[p:]
}
}
return x
}
[[[0 0 0] [0 0 0]] [[0 0 9] [0 0 0]]]
fn main() {
let m = 4;
let n = 6;
let p = 2;
let x = vec![vec![vec![0.0f64; p]; n]; m];
println!("{:#?}", x);
}
输出
[
[
[
0.0,
0.0,
],
[
0.0,
0.0,
],
[
0.0,
0.0,
],
[
0.0,
0.0,
],
[
0.0,
0.0,
],
[
0.0,
0.0,
],
],
[
[
0.0,
0.0,
],
[
0.0,
0.0,
],
[
0.0,
0.0,
],
[
0.0,
0.0,
],
[
0.0,
0.0,
],
[
0.0,
0.0,
],
],
[
[
0.0,
0.0,
],
[
0.0,
0.0,
],
[
0.0,
0.0,
],
[
0.0,
0.0,
],
[
0.0,
0.0,
],
[
0.0,
0.0,
],
],
[
[
0.0,
0.0,
],
[
0.0,
0.0,
],
[
0.0,
0.0,
],
[
0.0,
0.0,
],
[
0.0,
0.0,
],
[
0.0,
0.0,
],
],
]
fn main() {
const M: usize = 4;
const N: usize = 6;
const P: usize = 2;
let x = [[[0.0f64; P]; N]; M];
println!("{:#?}", x);
}
输出
[
[
[
0.0,
0.0,
],
[
0.0,
0.0,
],
[
0.0,
0.0,
],
[
0.0,
0.0,
],
[
0.0,
0.0,
],
[
0.0,
0.0,
],
],
[
[
0.0,
0.0,
],
[
0.0,
0.0,
],
[
0.0,
0.0,
],
[
0.0,
0.0,
],
[
0.0,
0.0,
],
[
0.0,
0.0,
],
],
[
[
0.0,
0.0,
],
[
0.0,
0.0,
],
[
0.0,
0.0,
],
[
0.0,
0.0,
],
[
0.0,
0.0,
],
[
0.0,
0.0,
],
],
[
[
0.0,
0.0,
],
[
0.0,
0.0,
],
[
0.0,
0.0,
],
[
0.0,
0.0,
],
[
0.0,
0.0,
],
[
0.0,
0.0,
],
],
]
28. Sort by a property
Sort elements of array-like collection items in ascending order of x.p, where p is a field of the type Item of the objects in items.
按x->p的升序对类似数组的集合项的元素进行排序，其中p是项中对象的项类型的字段。
package main
import "fmt"
import "sort"
type Item struct {
label string
p int
lang string
}
type ItemPSorter []Item
func (s ItemPSorter) Len() int { return len(s) }
func (s ItemPSorter) Less(i, j int) bool { return s[i].p < s[j].p }
func (s ItemPSorter) Swap(i, j int) { s[i], s[j] = s[j], s[i] }
func sortItems(items []Item) {
sorter := ItemPSorter(items)
sort.Sort(sorter)
}
func main() {
items := []Item{
{"twelve", 12, "english"},
{"six", 6, "english"},
{"eleven", 11, "english"},
{"zero", 0, "english"},
{"two", 2, "english"},
}
fmt.Println("Unsorted: ", items)
sortItems(items)
fmt.Println("Sorted: ", items)
}
Unsorted: [{twelve 12 english} {six 6 english} {eleven 11 english} {zero 0 english} {two 2 english}]
Sorted: [{zero 0 english} {two 2 english} {six 6 english} {eleven 11 english} {twelve 12 english}]
or
package main
import "fmt"
import "sort"
type Item struct {
label string
p int
lang string
}
func main() {
items := []Item{
{"twelve", 12, "english"},
{"six", 6, "english"},
{"eleven", 11, "english"},
{"zero", 0, "english"},
{"two", 2, "english"},
}
fmt.Println("Unsorted: ", items)
less := func(i, j int) bool {
return items[i].p < items[j].p
}
sort.Slice(items, less)
fmt.Println("Sorted: ", items)
}
Unsorted: [{twelve 12 english} {six 6 english} {eleven 11 english} {zero 0 english} {two 2 english}]
Sorted: [{zero 0 english} {two 2 english} {six 6 english} {eleven 11 english} {twelve 12 english}]
#[derive(Debug)]
struct Foo {
p: i32,
}
fn main() {
let mut items = vec![Foo { p: 3 }, Foo { p: 1 }, Foo { p: 2 }, Foo { p: 4 }];
items.sort_by(|a, b| a.p.cmp(&b.p));
println!("{:?}", items);
}
输出
[Foo { p: 1 }, Foo { p: 2 }, Foo { p: 3 }, Foo { p: 4 }]
or
#[derive(Debug)]
struct Foo {
p: i32,
}
fn main() {
let mut items = vec![Foo { p: 3 }, Foo { p: 1 }, Foo { p: 2 }, Foo { p: 4 }];
items.sort_by_key(|x| x.p);
println!("{:?}", items);
}
输出
[Foo { p: 1 }, Foo { p: 2 }, Foo { p: 3 }, Foo { p: 4 }]
29. Remove item from list, by its index
Remove i-th item from list items. This will alter the original list or return a new list, depending on which is more idiomatic. Note that in most languages, the smallest valid value for i is 0.
从列表项中删除第I项。 这将改变原来的列表或返回一个新的列表，这取决于哪个更习惯。 请注意，在大多数语言中，I的最小有效值是0。
package main
import (
"fmt"
)
func main() {
items := []string{"a", "b", "c", "d", "e", "f"}
fmt.Println(items)
i := 2
items = append(items[:i], items[i+1:]...)
fmt.Println(items)
}
[a b c d e f]
[a b d e f]
or
copy(items[i:], items[i+1:])
items[len(items)-1] = nil
items = items[:len(items)-1]
fn main() {
let mut v = vec![1, 2, 3];
assert_eq!(v.remove(1), 2);
assert_eq!(v, [1, 3]);
}
30. Parallelize execution of 1000 independent tasks
Launch the concurrent execution of procedure f with parameter i from 1 to 1000. Tasks are independent and f(i) doesn't return any value. Tasks need not run all at the same time, so you may use a pool.
用参数I从1到1000启动程序f的并发执行。 任务是独立的，f(i)不返回值。 任务不需要同时运行，所以可以使用pools
import "sync"
wg := sync.WaitGroup{}
wg.Add(1000)
for i := 1; i <= 1000; i++ {
go func(j int) {
f(j)
wg.Done()
}(i)
}
wg.Wait()
package main
import (
"fmt"
"math/rand"
"time"
)
func f(i int) {
d := rand.Int() % 10000
time.Sleep(time.Duration(d))
fmt.Printf("Hello %v\n", i)
}
func main() {
for i := 1; i <= 1000; i++ {
go f(i)
}
time.Sleep(4 * time.Second)
}
use std::thread;
fn main() {
let threads: Vec<_> = (0..1000).map(|i| thread::spawn(move || f(i))).collect();
for thread in threads {
thread.join();
}
}
fn f(i: i32) {
println!("{}", i);
}
or
extern crate rayon;
use rayon::prelude::*;
fn main() {
(0..1000).into_par_iter().for_each(f);
}
fn f(i: i32) {
println!("{}", i);
}
31. Recursive factorial (simple)
Create recursive function f which returns the factorial of non-negative integer i, calculated from f(i-1)
创建递归函数f，该函数返回从f(i-1)计算的非负整数I的阶乘
func f(i int) int {
if i == 0 {
return 1
}
return i * f(i-1)
}
package main
import (
"fmt"
)
func f(i int) int {
if i == 0 {
return 1
}
return i * f(i-1)
}
func main() {
for i := 0; i <= 10; i++ {
fmt.Printf("f(%d) = %d\n", i, f(i))
}
}
输出
f(0) = 1
f(1) = 1
f(2) = 2
f(3) = 6
f(4) = 24
f(5) = 120
f(6) = 720
f(7) = 5040
f(8) = 40320
f(9) = 362880
f(10) = 3628800
fn f(n: u32) -> u32 {
if n < 2 {
1
} else {
n * f(n - 1)
}
}
fn main() {
println!("{}", f(4 as u32));
}
输出
24
or
fn factorial(num: u64) -> u64 {
match num {
0 | 1=> 1,
_ => factorial(num - 1) * num,
}
}
fn main (){
println!("{}", factorial(0));
println!("{}", factorial(1));
println!("{}", factorial(2));
println!("{}", factorial(3));
println!("{}", factorial(4));
println!("{}", factorial(5));
}
输出
1
1
2
6
24
120
32. Integer exponentiation by squaring
Create function exp which calculates (fast) the value x power n. x and n are non-negative integers.
创建函数exp，计算(快速)x次方n的值。 x和n是非负整数。
package main
import "fmt"
func exp(x, n int) int {
switch {
case n == 0:
return 1
case n == 1:
return x
case n%2 == 0:
return exp(x*x, n/2)
default:
return x * exp(x*x, (n-1)/2)
}
}
func main() {
fmt.Println(exp(3, 5))
}
输出
243
fn exp(x: u64, n: u64) -> u64 {
match n {
0 => 1,
1 => x,
i if i % 2 == 0 => exp(x * x, n / 2),
_ => x * exp(x * x, (n - 1) / 2),
}
}
fn main() {
let x = 16;
let n = 4;
println!("{}", exp(x, n));
}
输出
65536
33. Atomically read and update variable
Assign variable x the new value f(x), making sure that no other thread may modify x between the read and the write.
为变量x分配新值f(x)，确保在读和写之间没有其他线程可以修改x。
package main
import (
"fmt"
"sync"
)
func main() {
var lock sync.RWMutex
x := 3
lock.Lock()
x = f(x)
lock.Unlock()
fmt.Println(x)
}
func f(i int) int {
return 2 * i
}
6
use std::sync::Mutex;
fn f(x: i32) -> i32 {
x + 1
}
fn main() {
let x = Mutex::new(0);
let mut x = x.lock().unwrap();
*x = f(*x);
println!("{:?}", *x);
}
输出
1
34. Create a set of objects
Declare and initialize a set x containing objects of type T.
声明并初始化一个包含t类型对象的集合x。
x := make(map[T]bool)
package main
import "fmt"
type T string
func main() {
// declare a Set (implemented as a map)
x := make(map[T]bool)
// add some elements
x["A"] = true
x["B"] = true
x["B"] = true
x["C"] = true
x["D"] = true
// remove an element
delete(x, "C")
for t, _ := range x {
fmt.Printf("x contains element %v \n", t)
}
}
x contains element D
x contains element A
x contains element B
or
x := make(map[T]struct{})
package main
import "fmt"
type T string
func main() {
// declare a Set (implemented as a map)
x := make(map[T]struct{})
// add some elements
x["A"] = struct{}{}
x["B"] = struct{}{}
x["B"] = struct{}{}
x["C"] = struct{}{}
x["D"] = struct{}{}
// remove an element
delete(x, "C")
for t, _ := range x {
fmt.Printf("x contains element %v \n", t)
}
}
x contains element B
x contains element D
x contains element A
use std::collections::HashSet;
fn main() {
let mut m = HashSet::new();
m.insert("a");
m.insert("b");
println!("{:?}", m);
}
输出
{"a", "b"}
35. First-class function : compose
Implement a function compose (A -> C) with parameters f (A -> B) and g (B -> C), which returns composition function g ∘ f
用参数f (A -> B)和g (B -> C)实现一个函数compose (A -> C)，返回composition函数g ∘ f
package main
import "fmt"
import "strconv"
func compose(f func(A) B, g func(B) C) func(A) C {
return func(x A) C {
return g(f(x))
}
}
func main() {
squareFromStr := compose(str2int, square)
fmt.Println(squareFromStr("12"))
}
type A string
type B int
type C int
func str2int(a A) B {
b, _ := strconv.ParseInt(string(a), 10, 32)
return B(b)
}
func square(b B) C {
return C(b * b)
}
144
fn compose<'a, A, B, C, G, F>(f: F, g: G) -> Box<Fn(A) -> C + 'a>
where F: 'a + Fn(A) -> B, G: 'a + Fn(B) -> C
{
Box::new(move |x| g(f(x)))
}
or
fn compose(f: impl Fn(A) -> B, g: impl Fn(B) -> C) -> impl Fn(A) -> C {
move |x| g(f(x))
}
fn main() {
let f = |x: u32| (x * 2) as i32;
let g = |x: i32| (x + 1) as f32;
let c = compose(f, g);
println!("{}", c(2));
}
输出
5
36. First-class function : generic composition
Implement a function compose which returns composition function g ∘ f for any functions f and g having exactly 1 parameter.
实现一个函数组合，该函数组合为任何恰好有1个参数的函数f和g返回组合函数g ∘ f。
package main
import "fmt"
func composeIntFuncs(f func(int) int, g func(int) int) func(int) int {
return func(x int) int {
return g(f(x))
}
}
func main() {
double := func(x int) int {
return 2 * x
}
addTwo := func(x int) int {
return x + 2
}
h := composeIntFuncs(double, addTwo)
for i := 0; i < 10; i++ {
fmt.Println(i, h(i), addTwo(double(i)))
}
}
0 2 2
1 4 4
2 6 6
3 8 8
4 10 10
5 12 12
6 14 14
7 16 16
8 18 18
9 20 20
fn compose<'a, A, B, C, G, F>(f: F, g: G) -> Box<Fn(A) -> C + 'a>
where F: 'a + Fn(A) -> B, G: 'a + Fn(B) -> C
{
Box::new(move |x| g(f(x)))
}
or
fn compose(f: impl Fn(A) -> B, g: impl Fn(B) -> C) -> impl Fn(A) -> C {
move |x| g(f(x))
}
fn main() {
let f = |x: u32| (x * 2) as i32;
let g = |x: i32| (x + 1) as f32;
let c = compose(f, g);
println!("{}", c(2));
}
输出
5
37. Currying
Transform a function that takes multiple arguments into a function for which some of the arguments are preset.
将一个接受多个参数的函数转换为一个预设了某些参数的函数。
package main
import (
"fmt"
"time"
)
type Company string
type Employee struct {
FirstName string
LastName string
}
func (e *Employee) String() string {
return "<" + e.FirstName + " " + e.LastName + ">"
}
type Payroll struct {
Company Company
Boss *Employee
Employee *Employee
StartDate time.Time
EndDate time.Time
Amount int
}
// Creates a blank payroll for a specific employee with specific boss in specific company
type PayFactory func(Company, *Employee, *Employee) Payroll
// Creates a blank payroll for a specific employee
type CustomPayFactory func(*Employee) Payroll
func CurryPayFactory(pf PayFactory, company Company, boss *Employee) CustomPayFactory {
return func(e *Employee) Payroll {
return pf(company, boss, e)
}
}
func NewPay(company Company, boss *Employee, employee *Employee) Payroll {
return Payroll{
Company: company,
Boss: boss,
Employee: employee,
}
}
func main() {
me := Employee{"Jack", "Power"}
// I happen to be head of the HR department of Richissim Inc.
var myLittlePayFactory CustomPayFactory = CurryPayFactory(NewPay, "Richissim", &me)
fmt.Println(myLittlePayFactory(&Employee{"Jean", "Dupont"}))
fmt.Println(myLittlePayFactory(&Employee{"Antoine", "Pol"}))
}
{Richissim 0001-01-01 00:00:00 +0000 UTC 0001-01-01 00:00:00 +0000 UTC 0}
{Richissim 0001-01-01 00:00:00 +0000 UTC 0001-01-01 00:00:00 +0000 UTC 0}
fn add(a: u32, b: u32) -> u32 {
a + b
}
fn main() {
let add5 = move |x| add(5, x);
let y = add5(12);
println!("{}", y);
}
输出
17
38. Extract a substring
Find substring t consisting in characters i (included) to j (excluded) of string s. Character indices start at 0 unless specified otherwise. Make sure that multibyte characters are properly handled.
查找由字符串s的字符I(包括)到j(不包括)组成的子字符串t。 除非另有说明，字符索引从0开始。 确保正确处理多字节字符。
package main
import "fmt"
func main() {
s := "hello, utf-8 문자들"
i, j := 7, 15
t := string([]rune(s)[i:j])
fmt.Println(t)
}
utf-8 문자
extern crate unicode_segmentation;
use unicode_segmentation::UnicodeSegmentation;
fn main() {
let s = "Lorem Ipsüm Dolor";
let (i, j) = (6, 11);
let t = s.graphemes(true).skip(i).take(j - i).collect::<String>();
println!("{}", t);
}
输出
Ipsüm
or
use substring::Substring;
let t = s.substring(i, j);
39. Check if string contains a word
Set boolean ok to true if string word is contained in string s as a substring, or to false otherwise.
如果字符串单词作为子字符串包含在字符串s中，则将布尔ok设置为true，否则设置为false。
package main
import (
"fmt"
"strings"
)
func main() {
s := "Let's dance the macarena"
word := "dance"
ok := strings.Contains(s, word)
fmt.Println(ok)
word = "car"
ok = strings.Contains(s, word)
fmt.Println(ok)
word = "duck"
ok = strings.Contains(s, word)
fmt.Println(ok)
}
true
true
false
fn main() {
let s = "Let's dance the macarena";
let word = "dance";
let ok = s.contains(word);
println!("{}", ok);
let word = "car";
let ok = s.contains(word);
println!("{}", ok);
let word = "duck";
let ok = s.contains(word);
println!("{}", ok);
}
输出
true
true
false
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