pattern-matching

问题 I was reading some Rust code and I came across this line if let Some(path) = env::args().nth(1) { Inside of this function fn main() { if let Some(path) = env::args().nth(1) { // Try reading the file provided by the path. let mut file = File::open(path).expect("Failed reading file."); let mut content = String::new(); file.read_to_string(&mut content); perform_conversion(content.as_str()).expect("Conversion failed."); } else { println!( "provide a path to a .cue file to be converted into a

问题 How do I fix the following errors? This expression was expected to have type 'string * Nullable * Nullable' but here has type 'VisitType' (Error occurs on "|AppointmentOnly(q.lastname, q.posting_time)). and Field 'appointmentTime' is not static (Error occurs on FsVisit.appointmentTime = q.appointment_time;). (These errors occur in my attempt to download records from a PostgreSQL database via WCF into F# client). type VisitType = | AppointmentOnly of name: string * postedTime: DateTime |

问题 I have data contained inside a Box , and would like to pattern match on it without accidentally copying the Box 's contents from the heap to the stack; how do I do that? Let's assume the following code: enum SomeEnum { SomeEntry, AnotherEntry, } fn main() { let boxed_value = Box::new(SomeEnum::AnotherEntry); match *boxed_value { SomeEnum::SomeEntry => {} SomeEnum::AnotherEntry => {} } } Does this copy the enum out of the box onto the stack and pattern match on that copy, or does it do the

问题 The aim is to parse a string into an array dictionary in javascript. For example this maybe the string that needs to be parsed "k=23:3/24:32b=43:532:45/3:3253" I would like that string to turn into a dictionary like so (Key - Value) k - 23:3/24:32 b - 43:532:45/3:3253 My initial idea was to search for [a-Z]\*.* and split it into matches using regex. However, I do not think this would work as this would also bring over b which is not what I want. Also, I was not able to get this to work (I'm

问题 consider examples below : Example 1 : str1 = "wow...it looks amazing" str2 = "looks amazi" You see that amazi is close to amazing , str2 is mistyped, i wanted to write a program that will tell me that amazi is close to amazing then in str2 i will replace amazi with amazing Example 2 : str1 = "is looking good" str2 = "looks goo" In this case updated str2 will be "looking good" Example 3 : str1 = "you are really looking good" str2 = "lok goo" In this case str2 will be "good" as lok is not close

问题 In particular with respect to pattern matching and case classes. Consider the following: abstract class Expr case class Var(name: String) extends Expr case class Number(num: Double) extends Expr case class UnOp(operator: String, arg: Expr) extends Expr case class BinOp(operator: String, left: Expr, right: Expr) extends Expr object Expr { def simplify(expr: Expr): Expr = expr match { // Some basic simplification rules... case UnOp("-", UnOp("-", e)) => simplify(e) // Double negation case BinOp

问题 In particular with respect to pattern matching and case classes. Consider the following: abstract class Expr case class Var(name: String) extends Expr case class Number(num: Double) extends Expr case class UnOp(operator: String, arg: Expr) extends Expr case class BinOp(operator: String, left: Expr, right: Expr) extends Expr object Expr { def simplify(expr: Expr): Expr = expr match { // Some basic simplification rules... case UnOp("-", UnOp("-", e)) => simplify(e) // Double negation case BinOp

问题 I am working on a time series data. The data available is multi-variate. So for every instance of time there are three data points available. Format: | X | Y | Z | So one time series data in above format would be generated real time. I am trying to find a good match of this real time generated time series within another time series base data, which is already stored (which is much larger in size and was collected at a different frequency). If I apply standard DTW to each of the series (X,Y,Z)

问题 Hope you can help me with something. Thanks to @mklement0 I've gotten a great script matching the most basic, initial pattern for words in alphabetical order. However what's missing is a full text search and select. An example of current script with a small sample of a few words within a Words.txt file: App Apple Apply Sword Swords Word Words Becomes: App Sword Word This is great as it really narrows down to a basic pattern per line! However the result of it going line by line there is still

问题 Hope you can help me with something. Thanks to @mklement0 I've gotten a great script matching the most basic, initial pattern for words in alphabetical order. However what's missing is a full text search and select. An example of current script with a small sample of a few words within a Words.txt file: App Apple Apply Sword Swords Word Words Becomes: App Sword Word This is great as it really narrows down to a basic pattern per line! However the result of it going line by line there is still