Rust vs Go:常用语法对比(二)

techdashen

2024-04-23 帮助1人

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

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

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.

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

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]]

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

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

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

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

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

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}]

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 }]

#[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]

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);
}

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

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

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

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)))
}

fn compose<A, B, C>(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)))
 }
}

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)))
}

fn compose<A, B, C>(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 <Jack Power> <Jean Dupont> 0001-01-01 00:00:00  0000 UTC 0001-01-01 00:00:00  0000 UTC 0}
{Richissim <Jack Power> <Antoine Pol> 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

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

这篇好文章是转载于：学新通技术网

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