如何在Rust中组合if let和match表达式

huangapple
go评论97阅读模式
英文:

How to combine if let match expression in rust

问题

Here is the translated code portion:

  1. fn main() {
  2.     println!("\n欢迎。这是温度转换器");
  3.     println!("我可以处理华氏度、摄氏度和开尔文度");
  4.     println!("\n请输入要转换的值：");
  6.     loop {
  7.         let mut value = String::new();
  8.         std::io::stdin()
  9.             .read_line(&mut value)
  10.             .expect("读取输入失败");
  11.         let value: f32 = match value.trim().parse() {
  12.             Ok(num) => num,
  13.             Err(_) => {
  14.                 println!("请输入数值。");
  15.                 continue;
  16.             }
  17.         };
  19.         println!("谢谢，我已经获得了值：{}。", value);
  20.         println!("请提供其相应的度量单位。");
  21.         println!("K：开尔文    C：摄氏度    F：华氏度：");
  23.         let mut unit = String::new();
  24.         std::io::stdin()
  25.             .read_line(&mut unit)
  26.             .expect("读取输入失败");
  27.         let unit = unit.trim().to_uppercase();
  28.         let unit = match unit.as_str() {
  29.             "K" => "K",
  30.             "F" => "F",
  31.             "C" => "C",
  32.             _ => {
  33.                 println!("请输入K、F或C，分别表示开尔文、华氏度或摄氏度。");
  34.                 continue;
  35.             }
  36.         };
  38.         println!("谢谢您的输入。我看到您要将 {} 度 {} 进行转换。", value, unit);
  39.         println!("请稍候，我将提供所有可能的转换。\n这将很快完成。");
  41.         if unit == "K" {
  42.             let value_c = value - 273.15;
  43.             let value_f = (((value - 273.15) * 9.0) + (32.0 * 5.0)) / 5.0;
  44.             println!("{}{} 转换为：{}C 和 {}F", value, unit, value_c, value_f);
  45.             println!("感谢您使用温度转换器。很高兴为您提供帮助。再见！");
  46.             break;
  47.         } else if unit == "C" {
  48.             let value_k = value + 273.15;
  49.             let value_f = (value * (9.0 / 5.0)) + 32.0;
  50.             println!("{}{} 转换为：{}K 和 {}F", value, unit, value_k, value_f);
  51.             println!("感谢您使用温度转换器。很高兴为您提供帮助。再见！");
  52.             break;
  53.         } else if unit == "F" {
  54.             let value_k = (((value - 32.0) * 5.0) / 9.0) + 273.15;
  55.             let value_c = ((value - 32.0) * 5.0) / 9.0;
  56.             println!("{}{} 转换为：{}K 和 {}C", value, unit, value_k, value_c);
  57.             println!("感谢您使用温度转换器。很高兴为您提供帮助。再见！");
  58.             break;
  59.         }
  60.     }
  61. }

Please note that I've replaced the HTML entities (") with regular double quotes (") for readability.

英文:

//here is my code. It is a Temperature Converter that takes input for Kelvin, Celsius or Fahrenheit and outputs converted value for corresponding contrary units.

// Problem:

// it will ask value first, which must be number, so the loop restarts. this is OK
// it will then ask for unit, which must be k,c or f. Upon different entry, it does catches and print "input k for kelvin, c for celcius F for Fahrenheit"
// But input doesnot register and jumps to the begening of the loop asking for value in numbers.

//All in all i want to catch the unit variable with k,c or f else ask the user to do so, not jump to the begening of loop.

// i am learning rust so excuse me for anything out of the norm.

//Here is my main.rs:

  1. fn main() {
  2. println!("\nWelcome. This is Temperature-Converter\n");
  3. println!("I work with Fahrenheit, Celsius and Kelvin");
  4. println!("\nPlease Input the Value you want to convert: ");
  5. loop{    
  6. let mut value = String::new();
  7. std::io::stdin().read_line(&mut value).expect("Failed to read line");
  8. let value:f32 = match value.trim().parse(){
  9. Ok(num) => num,
  10. Err(_) => {
  11. println!("please input value in number(s).");
  12. continue;
  13. }
  14. };
  15. println!("Thank You, I have the value: {value}.\nPlease provide it's respective unit of measurement.");
  16. println!("K : for Kelvin    C : for Celsius     F : for Fahrenheit : ");
  17. let mut unit = String::new();
  18. std::io::stdin().read_line(&mut unit).expect("Failed to read line");
  19. let unit = unit.trim().to_uppercase();
  20. let unit = match unit.as_str() {
  21. "K"=>"K",
  22. "F"=>"F",
  23. "C"=>"C",
  24. _=>{
  25. println!("please input K, F or C for Kelvin, Fahrenheit or Celcius respectively.");
  26. continue;
  27. }
  28. };
  29. println!("Thank you for your input. I see that you want to convert {value} degree {unit}.");
  30. println!("Please wait while i provide all possible conversions.\nThis will be quick.");
  31. if unit == "K"{
  32. let value_c = value-273.15;
  33. let value_f = (((value-273.15)*9.0)+(32.0*5.0))/5.0;
  34. println!("{value}{unit} is converted to: {value_c}C and {value_f}F");
  35. println!("Thank You for using Temperature Conversior. It was a pleasure to assist you. Byee!!");
  36. break;
  37. }
  38. else if unit == "C"{
  39. let value_k = value+273.15;
  40. let value_f = (value*(9.0/5.0))+32.0;
  41. println!("{value}{unit} is converted to:{value_k}K and {value_f}F");
  42. println!("Thank You for using Temperature Conversior. It was a pleasure to assist you. Byee!!");
  43. break;
  44. }
  45. else if unit == "F"{
  46. let value_k = (((value-32.0)*5.0)/9.0)+273.15;
  47. let value_c = ((value-32.0)*5.0)/9.0;
  48. println!("{value}{unit} is Converted to: {value_k}K and {value_c}C");
  49. println!("Thank You for using Temperature-Converter. It was a pleasure to assist you. Byee!!");
  50. break;
  51. };
  52. }
  53. }

//i tried :

  1. if let unit = match unit.as_str() {
  2. "K"=>"K",
  3. "F"=>"F",
  4. "C"=>"C",
  5. _=>{println!("please input K, F or C for Kelvin, Fahrenheit or Celcius respectively.")}
  6. };

// In fact i am having hard time understanding "match" and scope and return value of "loop"

答案1

得分: 0

  1. 程序逻辑仍可简化，目前只处理了语法问题：
  3.     fn main() {
  4.         println!("\n欢迎。这是温度转换器\n");
  5.         println!("我可以处理华氏度、摄氏度和开尔文");
  6.         println!("\n请输入您想转换的值：");
  8.         loop {
  9.             let mut input = String::new();
  10.             let mut value = 0.0_f32;
  12.             match std::io::stdin().read_line(&mut input) {
  13.                 Ok(_) => {
  14.                     value = match input.trim().parse() {
  15.                         Ok(num) => num,
  16.                         Err(_) => {
  17.                             println!("请以数字形式输入值。");
  18.                             continue;
  19.                         }
  20.                     };
  21.                     println!("谢谢，我已经得到值：{value}。");
  22.                 }
  23.                 Err(_) => println!("读取行失败"),
  24.             }
  26.             println!("请提供相应的计量单位。");
  27.             println!("K：表示开尔文    C：表示摄氏度     F：表示华氏度：");
  29.             let mut unit;
  30.             loop {
  31.                 unit = String::new();
  32.                 match std::io::stdin().read_line(&mut unit) {
  33.                     Ok(_) => {
  34.                         unit = unit.trim().to_uppercase();
  35.                         match unit.as_str() {
  36.                             "K" | "F" | "C" => break,
  37.                             _ => println!("请分别输入 K、F 或 C，表示开尔文、华氏度或摄氏度。"),
  38.                         }
  39.                     }
  40.                     Err(_) => println!("读取行失败"),
  41.                 }
  42.             }
  44.             println!("感谢您的输入。我看到您想将 {value} 度 {unit} 进行转换。");
  45.             println!("请稍候，我将提供所有可能的转换。\n这将很快完成。");
  47.             if unit == "K" {
  48.                 let value_c = value - 273.15;
  49.                 let value_f = (((value - 273.15) * 9.0) + (32.0 * 5.0)) / 5.0;
  50.                 println!("{value}{unit} 转换为：{value_c} 摄氏度和 {value_f} 华氏度");
  51.                 println!("感谢使用温度转换器。很高兴能帮助您。再见！");
  52.                 break;
  53.             } else if unit == "C" {
  54.                 let value_k = value + 273.15;
  55.                 let value_f = (value * (9.0 / 5.0)) + 32.0;
  56.                 println!("{value}{unit} 转换为：{value_k} 开尔文和 {value_f} 华氏度");
  57.                 println!("感谢使用温度转换器。很高兴能帮助您。再见！");
  58.                 break;
  59.             } else if unit == "F" {
  60.                 let value_k = (((value - 32.0) * 5.0) / 9.0) + 273.15;
  61.                 let value_c = ((value - 32.0) * 5.0) / 9.0;
  62.                 println!("{value}{unit} 转换为：{value_k} 开尔文和 {value_c} 摄氏度");
  63.                 println!("感谢使用温度转换器。很高兴能帮助您。再见！");
  64.                 break;
  65.             };
  66.         }
  67.     }
英文:

The program logic can still be simplified, for now only the syntactical problems are dealt with here:

  1. fn main() {
  2. println!("\nWelcome. This is Temperature-Converter\n");
  3. println!("I work with Fahrenheit, Celsius and Kelvin");
  4. println!("\nPlease Input the Value you want to convert: ");
  5. loop {
  6. let mut input = String::new();
  7. let mut value = 0.0_f32;
  8. match std::io::stdin().read_line(&mut input) {
  9. Ok(_) => {
  10. value = match input.trim().parse() {
  11. Ok(num) => num,
  12. Err(_) => {
  13. println!("please input value in number(s).");
  14. continue;
  15. }
  16. };
  17. println!("Thank You, I have the value: {value}.");
  18. }
  19. Err(_) => println!("Failed to read line"),
  20. }
  21. println!("Please provide it's respective unit of measurement.");
  22. println!("K: for Kelvin    C: for Celsius     F: for Fahrenheit : ");
  23. let mut unit;
  24. loop {
  25. unit = String::new();
  26. match std::io::stdin().read_line(&mut unit) {
  27. Ok(_) => {
  28. unit = unit.trim().to_uppercase();
  29. match unit.as_str() {
  30. "K" | "F" | "C" => break,
  31. _ => println!("please input K, F or C for Kelvin, Fahrenheit or Celcius respectively."),
  32. }
  33. }
  34. Err(_) => println!("Failed to read line"),
  35. }
  36. }
  37. println!("Thank you for your input. I see that you want to convert {value} degree {unit}.");
  38. println!("Please wait while i provide all possible conversions.\nThis will be quick.");
  39. if unit == "K" {
  40. let value_c = value - 273.15;
  41. let value_f = (((value - 273.15) * 9.0) + (32.0 * 5.0)) / 5.0;
  42. println!("{value}{unit} is converted to: {value_c}C and {value_f}F");
  43. println!("Thank You for using Temperature Conversior. It was a pleasure to assist you. Byee!!");
  44. break;
  45. } else if unit == "C" {
  46. let value_k = value + 273.15;
  47. let value_f = (value * (9.0 / 5.0)) + 32.0;
  48. println!("{value}{unit} is converted to:{value_k}K and {value_f}F");
  49. println!("Thank You for using Temperature Conversior. It was a pleasure to assist you. Byee!!");
  50. break;
  51. } else if unit == "F" {
  52. let value_k = (((value - 32.0) * 5.0) / 9.0) + 273.15;
  53. let value_c = ((value - 32.0) * 5.0) / 9.0;
  54. println!("{value}{unit} is Converted to: {value_k}K and {value_c}C");
  55. println!("Thank You for using Temperature-Converter. It was a pleasure to assist you. Byee!!");
  56. break;
  57. };
  58. }
  59. }

答案2

得分: 0

Sure, here is the translated code:

  1. fn main() {
  2.     
  3.         println!("\n欢迎。这是温度转换器\n");
  4.         println!("我可以处理华氏度，摄氏度和开尔文");
  5.         println!("\n请输入您要转换的值：");
  6.         
  7.         let value: f32 = loop {
  8.             let mut value = String::new();
  9.             std::io::stdin()
  10.                 .read_line(&mut value)
  11.                 .expect("读取失败");
  12.             match value.trim().parse::<f32>() {
  13.                 Ok(num) => break num,
  14.                 Err(_) => {
  15.                     println!("请以数字输入值。");
  16.                 }
  17.             };
  18.         };
  19.         println!("谢谢，我有这个值：{value}。\n请提供它的相应测量单位。");
  20.         println!("K：开尔文    C：摄氏度     F：华氏度：");
  21.         
  22.         let unit = loop {
  23.             let mut unit = String::new();
  24.             std::io::stdin()
  25.                 .read_line(&mut unit)
  26.                 .expect("读取失败");
  27.             let unit = unit.trim().to_uppercase();
  28.             match &*unit {
  29.                 "K" | "F" | "C" => break unit,
  30.                 _ => {
  31.                     println!("请分别输入K，F或C，表示开尔文，华氏度或摄氏度。\n我不区分大小写。");
  32.                 }
  33.             };
  34.         };
  36.         if unit == "K" {
  37.             let value_c = value - 273.15;
  38.             let value_f = (((value - 273.15) * 9.0) + (32.0 * 5.0)) / 5.0;
  39.             println!("{value}{unit} 转换为：{value_c}摄氏度 和 {value_f}华氏度");
  40.             println!("感谢您使用温度转换器。很高兴能帮助您。再见！！");
  41.         }
  42.         else if unit == "C" {
  43.             let value_k = value + 273.15;
  44.             let value_f = (value * (9.0 / 5.0)) + 32.0;
  45.             println!("{value}{unit} 转换为：{value_k}开尔文 和 {value_f}华氏度");
  46.             println!("感谢您使用温度转换器。很高兴能帮助您。再见！！");
  47.         }
  48.         else if unit == "F" {
  49.             let value_k = (((value - 32.0) * 5.0) / 9.0) + 273.15;
  50.             let value_c = ((value - 32.0) * 5.0) / 9.0;
  51.             println!("{value}{unit} 转换为：{value_k}开尔文 和 {value_c}摄氏度");
  52.             println!("感谢您使用温度转换器。很高兴能帮助您。再见！！");
  53.         };
  55. }
英文:

Thanks for to user: Kaplan
i have just defined variables with loop and later break the loop with variable value out of the loop.

  1. fn main() {
  2. println!(&quot;\nWelcome. This is Temperature-Converter\n&quot;);
  3. println!(&quot;I work with Fahrenheit, Celsius and Kelvin&quot;);
  4. println!(&quot;\nPlease Input the Value you want to convert: &quot;);
  5. let value:f32 = loop{
  6. let mut value = String::new();
  7. std::io::stdin()
  8. .read_line(&amp;mut value)
  9. .expect(&quot;Failed to read line&quot;);
  10. match value.trim().parse::&lt;f32&gt;(){
  11. Ok(num) =&gt; break num,
  12. Err(_) =&gt; {
  13. println!(&quot;please input value in number(s).&quot;);}
  14. };
  15. };
  16. println!(&quot;Thank You, I have the value: {value}.\nPlease provide it&#39;s respective unit of measurement.&quot;);
  17. println!(&quot;K : for Kelvin    C : for Celsius     F : for Fahrenheit : &quot;);
  18. let unit = loop{
  19. let mut unit = String::new();
  20. std::io::stdin()
  21. .read_line(&amp;mut unit)
  22. .expect(&quot;Failed to read line&quot;);
  23. let unit = unit.trim().to_uppercase();
  24. match &amp;*unit{
  25. &quot;K&quot; | &quot;F&quot; | &quot;C&quot; =&gt; break unit,
  26. _=&gt;{
  27. println!(&quot;Please input K, F or C for Kelvin, Fahrenheit or Celsius respectively.\nI am not case sensitive.&quot;);
  28. }
  29. };
  30. };
  31. if unit == &quot;K&quot;{
  32. let value_c = value-273.15;
  33. let value_f = (((value-273.15)*9.0)+(32.0*5.0))/5.0;
  34. println!(&quot;{value}{unit} is converted to: {value_c}C and {value_f}F&quot;);
  35. println!(&quot;Thank You for using Temperature Conversior. It was a pleasure to assist you. Byee!!&quot;);
  36. }
  37. else if unit == &quot;C&quot;{
  38. let value_k = value+273.15;
  39. let value_f = (value*(9.0/5.0))+32.0;
  40. println!(&quot;{value}{unit} is converted to:{value_k}K and {value_f}F&quot;);
  41. println!(&quot;Thank You for using Temperature Conversior. It was a pleasure to assist you. Byee!!&quot;);
  42. }
  43. else if unit == &quot;F&quot;{
  44. let value_k = (((value-32.0)*5.0)/9.0)+273.15;
  45. let value_c = ((value-32.0)*5.0)/9.0;
  46. println!(&quot;{value}{unit} is Converted to: {value_k}K and {value_c}C&quot;);
  47. println!(&quot;Thank You for using Temperature-Converter. It was a pleasure to assist you. Byee!!&quot;);
  48. };
  49. }

huangapple
  • 本文由 发表于 2023年5月18日 06:12:35
  • 转载请务必保留本文链接：https://go.coder-hub.com/76276513.html
  • match
  • rust
匿名

发表评论

匿名网友

:?: :razz: :sad: :evil: :!: :smile: :oops: :grin: :eek: :shock: :???: :cool: :lol: :mad: :twisted: :roll: :wink: :idea: :arrow: :neutral: :cry: :mrgreen:

确定