141. Iterate in sequence over two lists
Iterate in sequence over the elements of the list items1 then items2. For each iteration print the element.
依次迭代两个列表 依次迭代列表项1和项2的元素。每次迭代打印元素。
package main import ( "fmt" ) func main() { items1 := []string{"a", "b", "c"} items2 := []string{"A", "B", "C"} for _, v := range items1 { fmt.Println(v) } for _, v := range items2 { fmt.Println(v) } }
a b c A B C
fn main() { let item1 = vec!["1", "2", "3"]; let item2 = vec!["a", "b", "c"]; for i in item1.iter().chain(item2.iter()) { print!("{} ", i); } }
142. Hexadecimal digits of an integer
Assign to string s the hexadecimal representation (base 16) of integer x.
E.g. 999 -> "3e7"
将整数x的十六进制表示(16进制)赋给字符串s。
package main import "fmt" import "strconv" func main() { x := int64(999) s := strconv.FormatInt(x, 16) fmt.Println(s) }
or
package main import ( "fmt" "math/big" ) func main() { x := big.NewInt(999) s := fmt.Sprintf("%x", x) fmt.Println(s) }
fn main() { let x = 999; let s = format!("{:X}", x); println!("{}", s); let s = format!("{:x}", x); println!("{}", s); }
{:X} produces uppercase hex. {:x} produces lowercase hex.
3E7 3e7
143. Iterate alternatively over two lists
Iterate alternatively over the elements of the list items1 and items2. For each iteration, print the element.
Explain what happens if items1 and items2 have different size.
交替迭代两个列表
package main import ( "fmt" ) func main() { items1 := []string{"a", "b"} items2 := []string{"A", "B", "C"} for i := 0; i < len(items1) || i < len(items2); i++ { if i < len(items1) { fmt.Println(items1[i]) } if i < len(items2) { fmt.Println(items2[i]) } } }
a A b B C
extern crate itertools; use itertools::izip; fn main() { let items1 = [5, 15, 25]; let items2 = [10, 20, 30]; for pair in izip!(&items1, &items2) { println!("{}", pair.0); println!("{}", pair.1); } }
5 10 15 20 25 30
144. Check if file exists
Set boolean b to true if file at path fp exists on filesystem; false otherwise.
Beware that you should never do this and then in the next instruction assume the result is still valid, this is a race condition on any multitasking OS.
检查文件是否存在
package main import ( "fmt" "io/ioutil" "os" ) func main() { fp := "foo.txt" _, err := os.Stat(fp) b := !os.IsNotExist(err) fmt.Println(fp, "exists:", b) fp = "bar.txt" _, err = os.Stat(fp) b = !os.IsNotExist(err) fmt.Println(fp, "exists:", b) } func init() { ioutil.WriteFile("foo.txt", []byte(`abc`), 0644) }
There's no specific existence check func in standard library, so we have to inspect an error return value.
foo.txt exists: true bar.txt exists: false
fn main() { let fp = "/etc/hosts"; let b = std::path::Path::new(fp).exists(); println!("{}: {}", fp, b); let fp = "/etc/kittens"; let b = std::path::Path::new(fp).exists(); println!("{}: {}", fp, b); }
/etc/hosts: true /etc/kittens: false
145. Print log line with datetime
Print message msg, prepended by current date and time.
Explain what behavior is idiomatic: to stdout or stderr, and what the date format is.
打印带时间的日志
package main import "log" func main() { msg := "Hello, playground" log.Println(msg) // The date is fixed in the past in the Playground, never mind. } // See http://www.programming-idioms.org/idiom/145/print-log-line-with-date/1815/go
fn main() { let msg = "Hello"; eprintln!("[{}] {}", humantime::format_rfc3339_seconds(std::time::SystemTime::now()), msg); }
146. Convert string to floating point number
Extract floating point value f from its string representation s
字符串转换为浮点型
package main import ( "fmt" "strconv" ) func main() { s := "3.1415926535" f, err := strconv.ParseFloat(s, 64) fmt.Printf("%T, %v, err=%v\n", f, f, err) } // // http://www.programming-idioms.org/idiom/146/convert-string-to-floating-point-number/1819/go //
fn main() { let s = "3.14159265359"; let f = s.parse::<f32>().unwrap(); println!("{}² = {}" , f, f * f); }
or
fn main() { let s = "3.14159265359"; let f: f32 = s.parse().unwrap(); println!("{}² = {}", f, f * f); }
147. Remove all non-ASCII characters
Create string t from string s, keeping only ASCII characters
移除所有的非ASCII字符
package main import ( "fmt" "regexp" ) func main() { s := "dæmi : пример : příklad : thí dụ" re := regexp.MustCompile("[[:^ascii:]]") t := re.ReplaceAllLiteralString(s, "") fmt.Println(t) }
or
package main import ( "fmt" "strings" "unicode" ) func main() { s := "5#∑∂ƒ∞645eyfu" t := strings.Map(func(r rune) rune { if r > unicode.MaxASCII { return -1 } return r }, s) fmt.Println(t) }
fn main() { println!("{}", "do👍ot".replace(|c: char| !c.is_ascii(), "")) }
or
fn main() { println!("{}", "do👍ot".replace(|c: char| !c.is_ascii(), "")) }
148. Read list of integers from stdin
Read a list of integer numbers from the standard input, until EOF.
从stdin(标准输入)中读取整数列表
package main import ( "bufio" "fmt" "log" "strconv" "strings" ) func main() { var ints []int s := bufio.NewScanner(osStdin) s.Split(bufio.ScanWords) for s.Scan() { i, err := strconv.Atoi(s.Text()) if err == nil { ints = append(ints, i) } } if err := s.Err(); err != nil { log.Fatal(err) } fmt.Println(ints) } // osStdin simulates os.Stdin var osStdin = strings.NewReader(` 11 22 33 `)
use std::{ io::{self, Read}, str::FromStr, }; // dummy io::stdin fn io_stdin() -> impl Read { "123 456 789" .as_bytes() } fn main() -> io::Result<()> { let mut string = String::new(); io_stdin().read_to_string(&mut string)?; let result = string .lines() .map(i32::from_str) .collect::<Result<Vec<_>, _>>(); println!("{:#?}", result); Ok(()) }
Ok( [ 123, 456, 789, ], )
150. Remove trailing slash
Remove last character from string p, if this character is a slash /.
去除末尾的 /
package main import ( "fmt" "strings" ) func main() { p := "/usr/bin/" p = strings.TrimSuffix(p, "/") fmt.Println(p) }
fn main() { let mut p = String::from("Dddd/"); if p.ends_with('/') { p.pop(); } println!("{}", p); }
