题图来自 Rust vs. Golang: Which One is Better?[1]
182. Quine program
Output the source of the program.
输出程序的源代码
代码语言：javascript复制package main
import "fmt"
func main() {
fmt.Printf("%s%c%s%cn", s, 0x60, s, 0x60)
}
var s = `package main
import "fmt"
func main() {
fmt.Printf("%s%c%s%cn", s, 0x60, s, 0x60)
}
var s = `
输出：
代码语言：javascript复制package main
import "fmt"
func main() {
fmt.Printf("%s%c%s%cn", s, 0x60, s, 0x60)
}
var s = `package main
import "fmt"
func main() {
fmt.Printf("%s%c%s%cn", s, 0x60, s, 0x60)
}
var s = `
另一种写法：
//go:embed 入门[2]
Quine 是一种可以输出自身源码的程序。利用 go:embed 我们可以轻松实现 quine 程序：
代码语言：javascript复制package main
import (
_ "embed"
"fmt"
)
//go:embed quine.go
var src string
func main() {
fmt.Print(src)
}
fn main() {
let x = "fn main() {n let x = ";
let y = "print!("{}{:?};n let y = {:?};n {}", x, x, y, y)n}n";
print!("{}{:?};
let y = {:?};
{}", x, x, y, y)
}
输出：
代码语言：javascript复制fn main() {
let x = "fn main() {n let x = ";
let y = "print!("{}{:?};n let y = {:?};n {}", x, x, y, y)n}n";
print!("{}{:?};
let y = {:?};
{}", x, x, y, y)
}
or
代码语言：javascript复制fn main(){print!("{},{0:?})}}","fn main(){print!("{},{0:?})}}"")}
输出：
fn main(){print!("{},{0:?})}}","fn main(){print!("{},{0:?})}}"")}
184. Tomorrow
Assign to variable t a string representing the day, month and year of the day after the current date.
明天的日期
代码语言：javascript复制import "time"
t := time.Now().Add(24 * time.Hour).Format("2006-01-02")
fn main() {
let t = chrono::Utc::now().date().succ().to_string();
println!("{}", t);
}
2021-07-18UTC
185. Execute function in 30 seconds
Schedule the execution of f(42) in 30 seconds.
30秒内执行功能
代码语言：javascript复制import "time"
timer := time.AfterFunc(
30*time.Second,
func() {
f(42)
})
or
代码语言：javascript复制package main
import (
"fmt"
"time"
)
func main() {
fmt.Println("Scheduling f(42)")
go func() {
time.Sleep(3 * time.Second)
f(42)
}()
// Poor man's waiting of completion of f.
// Don't do this in prod, use proper synchronization instead.
time.Sleep(4 * time.Second)
}
func f(i int) {
fmt.Println("Received", i)
}
Scheduling f(42)
use std::time::Duration;
use std::thread::sleep;
sleep(Duration::new(30, 0));
f(42);
186. Exit program cleanly
Exit a program cleanly indicating no error to OS
干净地退出程序
代码语言：javascript复制package main
import (
"fmt"
"os"
)
func main() {
fmt.Println("A")
os.Exit(0)
fmt.Println("B")
}
A
or
代码语言：javascript复制package main
import (
"fmt"
"os"
)
func main() {
process1()
process2()
process3()
}
func process1() {
fmt.Println("process 1")
}
func process2() {
fmt.Println("process 2")
defer fmt.Println("A")
defer os.Exit(0)
defer fmt.Println("B")
fmt.Println("C")
}
func process3() {
fmt.Println("process 3")
}
process 1
process 2
C
B
use std::process::exit;
fn main() {
println!("A");
exit(0);
println!("B");
}
A
189. Filter and transform list
Produce a new list y containing the result of function T applied to all elements e of list x that match the predicate P.
过滤和转换列表
代码语言：javascript复制package main
import (
"fmt"
)
func P(e int) bool {
// Predicate "is even"
return e%2 == 0
}
type Result = int
func T(e int) Result {
// Transformation "square"
return e * e
}
func main() {
x := []int{4, 5, 6, 7, 8, 9, 10}
var y []Result
for _, e := range x {
if P(e) {
y = append(y, T(e))
}
}
fmt.Println(y)
}
[16 36 64 100]
let y = x.iter()
.filter(P)
.map(T)
.collect::<Vec<_>>();
190. Call an external C function
Declare an external C function with the prototype void foo(double *a, int n); and call it, passing an array (or a list) of size 10 to a and 10 to n. Use only standard features of your language.
调用外部C函数
代码语言：javascript复制// void foo(double *a, int n);
// double a[] = {0, 1, 2, 3, 4, 5, 6, 7, 8, 9};
import "C"
C.foo(C.a, 10)
extern "C" {
/// # Safety
///
/// `a` must point to an array of at least size 10
fn foo(a: *mut libc::c_double, n: libc::c_int);
}
let mut a = [0.0, 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0, 9.0];
let n = 10;
unsafe {
foo(a.as_mut_ptr(), n);
}
191. Check if any value in a list is larger than a limit
Given a one-dimensional array a, check if any value is larger than x, and execute the procedure f if that is the case
检查列表中是否有任何值大于限制
代码语言：javascript复制package main
import (
"fmt"
)
func f() {
fmt.Println("Larger found")
}
func main() {
a := []int{1, 2, 3, 4, 5}
x := 4
for _, v := range a {
if v > x {
f()
break
}
}
}
Larger found
fn main() {
let a = [5, 6, 8, -20, 9, 42];
let x = 35;
if a.iter().any(|&elem| elem > x) {
f()
}
let x = 50;
if a.iter().any(|&elem| elem > x) {
g()
}
}
fn f() {
println!("F")
}
fn g() {
println!("G")
}
F
192. Declare a real variable with at least 20 digits
Declare a real variable a with at least 20 digits; if the type does not exist, issue an error at compile time.
声明一个至少有20位数字的实变量
代码语言：javascript复制package main
import (
"fmt"
"math/big"
)
func main() {
a, _, err := big.ParseFloat("123456789.123456789123465789", 10, 200, big.ToZero)
if err != nil {
panic(err)
}
fmt.Println(a)
}
1.234567891234567891234657889999999999999999999999999999999999e 08
use rust_decimal::Decimal;
use std::str::FromStr;
let a = Decimal::from_str("1234567890.123456789012345").unwrap();
197. Get a list of lines from a file
Retrieve the contents of file at path into a list of strings lines, in which each element is a line of the file.
从文件中获取行列表.将文件路径中的内容检索到字符串行列表中，其中每个元素都是文件的一行。
代码语言：javascript复制package main
import (
"fmt"
"io/ioutil"
"log"
"strings"
)
func readLines(path string) ([]string, error) {
b, err := ioutil.ReadFile(path)
if err != nil {
return nil, err
}
lines := strings.Split(string(b), "n")
return lines, nil
}
func main() {
lines, err := readLines("/tmp/file1")
if err != nil {
log.Fatalln(err)
}
for i, line := range lines {
fmt.Printf("line %d: %sn", i, line)
}
}
func init() {
data := []byte(`foo
bar
baz`)
err := ioutil.WriteFile("/tmp/file1", data, 0644)
if err != nil {
log.Fatalln(err)
}
}
line 0: foo
line 1: bar
line 2: baz
use std::fs::File;
use std::io::prelude::*;
use std::io::BufReader;
fn main() {
let path = "/etc/hosts";
let lines = BufReader::new(File::open(path).unwrap())
.lines()
.collect::<Vec<_>>();
println!("{:?}", lines);
}
[Ok("127.0.0.1tlocalhost"), Ok("::1tlocalhost ip6-localhost ip6-loopback"), Ok("fe00::0tip6-localnet"), Ok("ff00::0tip6-mcastprefix"), Ok("ff02::1tip6-allnodes"), Ok("ff02::2tip6-allrouters")]
198. Abort program execution with error condition
Abort program execution with error condition x (where x is an integer value)
出现错误情况时中止程序执行
代码语言：javascript复制package main
import (
"os"
)
func main() {
x := 1
os.Exit(x)
}
Program exited: status 1.
use std::process;
process::exit(x);
200. Return hypotenuse
Returns the hypotenuse h of the triangle where the sides adjacent to the square angle have lengths x and y.
返回三角形的斜边h，其中与直角相邻的边的长度为x和y。
代码语言：javascript复制package main
import (
"fmt"
"math"
)
func main() {
x := 1.0
y := 1.0
h := math.Hypot(x, y)
fmt.Println(h)
}
1.4142135623730951
fn main() {
let (x, y) = (1.0, 1.0);
let h = hypot(x, y);
println!("{}", h);
}
fn hypot(x: f64, y: f64) -> f64 {
let num = x.powi(2) y.powi(2);
num.powf(0.5)
}
1.4142135623730951
参考资料
[1]
Rust vs. Golang: Which One is Better?: https://www.emizentech.com/blog/rust-vs-golang.html
[2]
//go:embed 入门: https://taoshu.in/go/how-to-use-go-embed.html
